IMT - Experienced Employees' Handbook     Advanced training. Minor notes.

Turn 1
HQ Screen
Increase techs.
Note: in one game, with 2 million starting population, I decided to take a risk and concentrate purely on Planet Tech to get a Metals Exchange as quickly as possible. As a result I got planet tech 6 on turn 7, a Metals Exchange on turn 8 and a sudden boost of 33,000mc on turn 9. However, my hull tech was still just tech 2 at that stage and I would have been easy meat if a hyperjump-race had decided to attack at that point!
Choose a suitable ID.
Taxes should be set to Ultra Conservative to maximise happiness of colonists (and, later, Natives if you get any).

Base
Build a Government Centre.
Build as many factories as possible (use supplies off the ships)
Set factory output to max (10,000)
You can't build terraformers, but some games' starting scripts may give you some on your homeworl.d. If so, don't bother turning them on. They burn supplies until  the temperature is optimised, and IMT doesn't care about climate.
Use your Air Attack Base to form your starting fighters into free flying Wings at your homeworld. Split the Bismuth Zepplins into three Wings with no DDD's or SSS's in them. Build three Wings of 10 SSS's: these will be docked with Sheffields in a couple of turns.
Build a couple of Midshipmens' Gigs, with the good starting engines.  These will stake claims on nearby planets, and scout.
Build 3 more Midshipmens' Gigs with rubbish engines (speed 15). These will be expendable border guards.
Don't bother with the Ordnance Plant - it's cheaper to make Ord with the Metro's Mobile Ord Plant when you get hull tech 4. You need your supplies for factory building right now.
Set Base Attack Mode to Peaceful to maximise growth.

Ships
Transport almost all food down to the base (leave 20 on each ship for colonies). You can't build farms - this food is all you've got until you can acquire more.
Send out the starting ships to find nearby native-rich worlds for a quick cash boost with Londons.  They should have a few (ie 30) supplies, 200-300mc and a full load of colonists. This is OK for building pod launchers. You don't need farms (or mines on most worlds), so no need to heavily settle worlds except ones with contraband. Use the Gotham and London to colonise nearby worlds. You might choose to keep the Gig's Gravitonic Accelerator off so as not to advertise your presence whilst you are weak (though test games show that it isn't too visible until other players get nearer, around turn 5).
Put a HG on board the London (and maybe the Veeps Gig to stop people Spying its hull plan).
From all ships, beam down most supplies to build as many factories as you can. This is to get as many cities going as possible, as quickly as possible, for cash.
Turn on "Repair ship" switches.
Turn on scanners.
Set Attack switches to Attack Enemy Ships, Sandcasters Fire on Ships and Fighters. Don't set Ram for these starting ships, they'e too light to benefit.

London:
Turn the Grav Well Generator ON from turn 1 and leave it on.
Transfer 200kT fuel onto the ship.
Set the attack switches / commands as you see fit. In some games, starting ships start with attack Off!
Send this ship out to form bases, etc. Turn on the Reticulan Med Lab so when it stumbles across natives, they begin turning into cash, supplies and food immediately. Ideally, it will find a native-rich world where the Reticulan Med Lab can start turning local natives into cash before the Rebels or Privateers find them and steal them with Native Dustoffs.  A London above a populous native world allows you to build a government centre there and pump cash directly into your central account. This lets you get planet tech to 6 quickly for the Metals Exchange, after which the natives are just a minor cash source(!), although you must ship the  food created by the Med Lab home.
This London should be armed with a sandcaster and turbolasers for a fighter-killer and homeworld defense ship. Set it to Attack Soft, Standoff Range 999, First Wave, random attack vector, "sandcasters fire only at fighters". It is also armed with phasors to kill incoming assault pods.
You must decide whether this ship is best used getting lots of start up cash by exploiting nearby natives, or defending your homeworld (The Evil Empire could attack as early as turn 8, for example).

Gotham:
Nothing special here. Use it to check out a nearby star or two, scoop up metals and take them home to be sold later. You may want this ship back at your home base later, to tow Sheffields.

Midshipman's Gig:
Use this ship as a scout and to form advance bases. If it finds natives, send the London to use its Reticulan Med Lab on them. And accumulating Chups will be useful later.
Unless you are in a small galaxy, you can use the Gravitonic Accelerator on turn 1: it is unlikely that anyone will be near enough to see your enhanced sensor image. If you are in a small galaxy, keep the Grav Accelerator switched off.
Turn "Attack Ground" OFF on your Veeps Gigs. Otherwise you will start border disputes unintentionally when you stumble into other players' bases! Veeps Gigs aren't hard enough to kill enemy bases, so there's no point..

Miscellaneous:
Send messages to other players - begin building relationships. You will need to trade for minelayers, food etc later.

Turn 2
Base
Use the factory output to build 5-10 cities each turn until you have one per 100,000 population. Don't worry about stunting population growth - food and happiness have a much larger effect.
Government Centre:  transfer cash to Central Account.
Turn on your Training Centres.
The Wings of Bismuths should be set to Auto Intercept Enemy Ships at speed 100, with attack setting "Quick Strike". Then if any passing Privateers or Borg probes get knocked out of hyperspace by the London, and are visible, hopefully they will be destroyed by the Wing the same turn. Ships coming out of hyperspace have practically no chance of scanning anything the same turn, so your core area's secrets will remain safe. But to prevent them chasing things seen a long way away, and zooming away from your HW and stranding themselves in deep space, reduce their auto-intercept range to 30.
Build ships.

Midshipmens' Gigs:
Scout for natives. Set up bases - grab territory to negotiate with, set up peripheral bases. Use the Grav Accs if necessary.
The slow Gigs whould radiate out to your borders. These are simply watching for trouble.

Turn 3
Sheffields:
Turn on their Devices to mine your homeworld  <--- dangerous , process ore, and increase its HD Stress. This will generate free metals in the planet's core. Don't overdo this on your homeworld, because planets with HD Stress >1000 can disintegrate. But you'll only be doing it for one turn while it waits for its "tow" to be built.

Turns 8+
Turn 8: some unpleasant beastliness begins round now as races with good starting ships (like, say, Robots- see Race-Specific Notes below) begin raiding. Compared to other races, IMT starts with very poor combat abilities except homeworld-created Wings.  You need to invest your superior cash in weapon and hull and engine techs to counter their superior combat abilities.
You should be approaching Planet Tech 6 and perhaps Hull Tech 6.
Begin towing pods of Chups towards other players' areas, or simply flinging them with pod launchers. Build Londons and send them off to harvest food (natives) with their Reticulan Light Beams.

Turn 10
Spying will be possible next turn, so set your Spy commands to sabotage alien bases etc.
Your homeworld is probably up to maximum happiness (300) now.

Long term
Rather than grab vast areas of territory, it is easier to move to an area, strip the minerals, harvest the population, turn the planets into asteroid fields to deny resources to others, and move on. Remember that you can reposition shipyards to permit easier attacks on a new front. You are like the Borg - a mobile plague which burns out an area and moves on. You have no need to expand over a huge area all at once; it is easier to maintain / defend half a dozen good, big worlds and drag them en masse to a new area rich in natural resources awaiting efficient garnering and selling.You can relocate to where the minerals are found more easily than most. Use the food you Harvest to grow new Chups, and scatter pods of them throughout a region you are leaving. Exploding the pods leaves the area infested with ravenous chups, so even the Privateer rock hoppers will be unable to set up major bases  in your wake.

First get the metals: Use the Sheffield Mining Platforms' HD Stress Amps [or Great Pyramids in the late game] to increase planets' HD stress. Planets generate a small amount of metals every turn, naturally. The quantity varies with HD Stress and increases exponentially above 100 [one hundred], so run it up to near  850. Above 1000, planets tend to disintegrate into asteroid belts, destroying bases. HD Stress fluctuates a bit anyway, which is why you only run it up to 850 - it gives you some reaction time in case of imminent disintegration.

A base's population will perish if a planet breaks up under them.

Once planets have disintegrated from hyperdimensional stress, the resulting rich asteroid field can still be mined. After being mined out, it can be reassembled into a somewhat unstable planet (with new minerals!) using the Protomatter Cannon on the Great Pyramid, though it will be many turns before you can afford Superweapon Tech 5. A planet can be cycled many times through the asteroid / planet / asteroid cycle, generating metals each time through the wonders of HD Stress Physics.

Combat

To galaxy comes new threat
Planets, Chupanoids, are our weapons
Only fools require muscle.

See also: tactical tips on the ship, fighter and mech pages on this website. But in general:  

Unlike most races, you  can go for a swarming strategy AND a few heavy ships.

Do not forget your Ramming Bonus, which helps the Sheffield, Great Western, VOF and GP against smaller ships.

Have your entire fleet arrive as one pack with one identical attack vector in the same wave.

One time the larger ships become really important is when there are lots of minefields. Minefield defences are hell on small ships and free Wings, which are vulnerable even when towed.

Most IMT Megacorp ships are designed primarily as big cheap freighters. They can carry lots of armour and some very large weapons, but in combat, they all have flaws and are not outstanding in quality. So concentrate on quantity, with a few big ships and planets thrown in to keep your enemies worried. And don't forget your Ramming bonus!

Tim sent me a Host code fragment to illustrate how Ramming works. This explains why a Gotham can't harm a ship with 3,000 point shields and lots of armour by Ramming:  Damage first has to get through shields, then armour, and gets reduced at each stage (though it can also wear down the shields and armour). Finally a little damage gets through to the hull, engines, and other systems.

Here are some key lines of Host code;

If ship is set to Ram
   And comes within X km of enemy
  Then <do Ram damage>
 But where X = 20 for most races, it is 100 km for race 818, IMT. In other words IMT ships are more LIKELY to Ram but get no BONUS.

      Damage to ship being rammed:
      vP = m2_cob(cid).hullmass * m2_cob(cid).speed
      vDam = vP * ( 100 / (m2_cob(tid).hullmass + 50) )    ...ie, proportional to ratio of rammer's hull mass / victim's hull mass

      '// Damage to the ship doing the ramming //
      vDam = vP * ( 100 / (m2_cob(cid).hullmass + 50) )    ...ie, a straight 2 * "max hull speed" if the rammer's hull mass is >>50, and worse for the rammer if they are a light craft.

Veeps Ashran Gildowan and Drew Sullivan did some work on Ramming and found a flaw in the code (Host 193). It seems there's a threshold max hull speed below which ships won't ram, probably related to these two lines of code:

v = 6 - mass / 100
v = v + Hull.MaxSpeed / 40

We suspect the beakpoint is 21.

Miscellaneous tips
If the Spindizzy ever works, people will pay to have planets moved. And not just to tow resources nearer to their homeworld. What would you pay IMT to tow your homeworld to safety as an enemy fleet approached? It is like having a Ground Chunnel device. But only IMT can use the spindizzy, so you have a monopoly...
If a planet's HD Stress has reached 950, it may be too late to turn off a Sheffield's scalar wave amp and laser mining drill. In one test game,  I switched off these devices because HD stress was 950, but the planet still blew up next turn with a reported HD Stress of 1031. I believe the devices must be switched off by Host AFTER they have worked, ie the host order-of-events is the opposite of what you expect.
Laser mining drills can mine asteroid belts, so don't worry too much if you blow up planets.
You can't build farms. But an ally can build them for you, then "GBA" the base to you. If you've got terraformers there to lock the climate onto 50 degrees, the farms will produce food.

Interesting fact from Tim: Will it be possible to have multiple planets in a solar system? This would avoid the need for the keep-your-4LY-distance rule for planets.