I must start by saying that although I am putting this information together for posting the majority has come from others in the Homeworld community. I do not remember all of the people who I should list as contributing but I will, at the end, list those who come to mind most prominently. The game does indeed have only 3 tactics that you can set the ships in BUT, these settings in and of themselves are not all the tactics possible in the game. You are limited only by your imagination.
Tactic 1 Evasive (key F2): This shunts power from the guns to the engines for faster movement and dodging of gun fire. This is also the least effective tactic if you want to do any damage when using strike craft, especially scouts. It has very little effect on the damage cap ships will do but on the plus side it keeps your ships firing only on the target you set. This setting for strike craft allows them to live longer in a fire fight but is mainly useful for making them stall the enemy.
Tactic 2 Neutral (key F3 and default): This setting balances power between engine power and weapon power, giving a good middle ground for damage dealt and taken. A ship set to neutral will auto retaliate, that is fire on enemy ships in range or when fired upon. This is the setting all ships are set at when exiting the building facility (carrier or mother ship). If you want them to stay put you need to set them to evasive.
Tactic 3 Aggressive (key F4): This setting is best described as suicide running. The 'pilots' of strike craft do not seek to dodge any enemy fire, they 'run' head long right toward their target firing guns full bore. For cap ships this essentially makes them attack any enemy ship that attacks them, this will spread your fire over several different targets even when you want a single target to be the focus of concentrated fire. This setting is okay for cap ships in a fight between cap ships and fighters or corvettes, but will loose you the battle in a cap to cap fight.
Strike craft:
When using strike craft you can gain an advantage in a few ways, if your opponent is relatively inexperienced you can gain victory in strike craft fights by changing tactics at just the right time. All strike craft have attack runs, that is they approach their intended target firing on it, then as they pass they stop their firing to get far enough away to turn for a return run. If you start your run in aggressive your accuracy will be higher than your opponents thus you'll deal more damage, but you will come out the looser in the long run if you leave your ships unmanaged. As soon as your ships pass the ones you attack hit F2 evasive, this makes them turn on their heels and start an attack run again. As they start to fire hit F4 aggressive to get the higher firing rate back, you'll be hitting them in the rear so you have little fear of reprisal. This combined with the right formation can gain you victory.
Corvettes:
When using corvettes tactics become less effective if you don't manage them right, corvettes do not have attack runs so they usually circle their target as they lay waste to it. In this instance the smartest course of action is to go with a 'Wolf pack' scenario. The wolf pack is 9-12 light vettes supported by repair vettes or 2 support frigates. The vettes are set to F4 aggressive in wall formation, this keeps them in formation better than any other formation making it easier for them to be supported. The repair vettes or support frigates need to be set to F2 evasive to keep them repairing the corvettes and not auto retaliating. The wolf pack can have any vette but salvage in place of the light vette but mine layers are not suggested (we got better plans for them). In the pack configuration the heavy vette rules supreme. They have more punch and more armor that any other and will give you quiet a long run before being overwhelmed. A tip though, the smart thing for the opposition to do is take out the support first, if this happens set the pack to evasive, they'll start circling the target and present a harder target themselves, leave them to the attack checking back every 15-30 seconds to target a new ship.
Frigates:
Tactics with frigates are, in most cases, similar to capital and super capital in that for fire power damage dealing, the difference between the three settings is less obvious. The best thing I have found is to set the ships to evasive to prevent auto retaliation. The surest way to win an engagement between equal numbers is to concentrate fire. Hit one ship at a time so it goes down more quickly, always go for the smallest ion capable ships first. Ions deal an amazing amount of damage, when applied properly they are deadly. If you have a group of 5 assault frigates you can easily die if you take on say 2 ion frigates and 2 assault frigates, but then if you do things right you can be victorious as well. Assault frigates are one of the most maneuverable frigate class ships, set them to moving as they attack and they can avoid the ion frigates, provided you never put them in a formation. Setting cap ships in a formation limits their movement, the whole formation has to bear on the target before any will fire, if they are in no formation the ships start firing as soon as they can, increasing your damage potential enormously, plus it's easier to select a single ship out of a formation to concentrate fire on it, so your protecting your assets by keeping them together as close as possible.
Capital ships:
As above with frigates F2 evasive is best to avoid auto retaliation. so you can better concentrate fire on one ship at a time. The easiest way to make your cap ships form a tight clump without ordering a formation is to select them all, assign them to a group (I use 10) and issue several short distance moves in front of or behind the ms. They will all move to the same spot and create a tight bunch, do not press any formation keys, including F11 custom. The whole point of setting them in a tight bunch is to make it harder for your opponent to select the same ship in your group and to have your ships turn and fire in the shortest time possible. With no formation your ships will fire on the target as it comes into their respective field of fire. This means no ship will wait for the last one to get in firing range before firing. That alone is worth the effort since you end up firing more often that the enemy.
I have more stuff to provide but I will do that at a later time, as I promised here are some of the people who have contributed to this information albeit inadvertently. Calaban, Cadfan, Major Freak (the Faq man), Vampyre, Several of the OMO bunch, Dynthoes, SirMolle, and many others I can not now think of.
regards, 1_Alpha(WON) aka Alpha_1(Relic forums)