One important technique for Stars ship design is the art of designing a ship type specifically in response to a known enemy ship type. This process is called ship counterdesign. Knowing how to counterdesign, and how to avoid making your own designs have easy counters, is an important part of stars expertise.
There are a great number of methods of counterdesign. This article is a discussion of some (most?) of them. But first, some detail on the guts of stars; understanding how some of these details work is necessary to understand why a method of counterdesign works.
Now, the actual counterdesign tips:
For example, if your enemy has a heavy, slow design, say myopic disruptors (range 1) on a BB, you can counterdesign by using blasters (range 2) and making sure your ship is lighter.
Note that no matter what the speed of the longer range design, it is hard to get many free shots out of longer range against very fast ships, since within a few turns they can always get to you by backing you up to the edge of the battle board. Hence, it is a design principle in stars to go with beams of at least range 2 if possible, and to always put beams on fast ships.
For example, say your enemy has invested in armored heavy blaster BBs. Armor is heavy. You might counter the design by using range 1 or even range 0 beam BBs or CAs, designed to be fast enough to close rapidly, and (if BB) not armored, so that they stay at least 30% lighter than the blaster BBs. Although your ships are individually considerably weaker than the blaster BBs, they are much cheaper.
Generally, trying to win with cheaper shorter range ships is not a strong method of counterdesign, but it is useful to know that it can work at least in theory. The WM PRT, with its unique battle cruiser hull, can often exploit this method of counterdesign against enemy battleship designs.
He who fires first often wins Stars battles. Stars weapons fire in order of their initiative, high to low. Weapon initiative comes from the weapons, the hull, and the computers on board. Thus, a typical counterdesign technique is to take the enemy design and add one more computer.
For example, one design sometimes seen from newer players is a BB with 6 supercomputers and one overthruster. This design can be countered by replacing the overthruster with another computer.
[Counter counterdesign: the first BBs built sometimes use all 7 possible slots for battle supercomputers. This design is costly, but cannot be "outinitiatived", at least until battle nexi or nubians appear.]
Initiative wars are particularly important in the parts of the game where damage from weapons is relatively high compared to the average defensive systems (armor and shields, jammers and beam deflectors) likely to be encountered. A typical midgame situation will have energy 10 or 14, weapons 20, and con 13, hence the main fleet warship will be BBs with 600 or 1050 shields, 2000-4200 armor, vs 16 or 20 doomsday missiles -- 4480 to 5600 damage, if all hit, and doubled once the shields are down. Even at the base 30% accuracy of the missiles, a combat between two such forces would last only two rounds; clearly, shooting first will be a big help.
In the high tech stars game, initiative is still important, but somewhat less so.
A typical case here is an early BB, say Juggs and 7 BSCs. A possible counter is a similar design using 3 BSCs and 4 jammer 20s. The enemy goes first, but with only 49.5% accuracy; your (unjammed) return fire has 87.4% accuracy. Assuming you have enough shields and armor to withstand the first volley, your much higher return accuracy should prove deadly. (Note, however, that this counter design itself has a superior counter-counter design: 4 BSC/3 Jam20... which is why it is not typically used; instead, players go immediately to the 4 BSC/3 Jam 20 design.)
On BBs, it is difficult to gain much of an edge, since you cannot add any more shields by removing armor. But with other hull types, you can. A typical newbie mistake in stars is using too much armor on warships.
Note that with most races, G is very tight until late in the game, since you need it for both factory-building and computers. Thus, you are unlikely to be able to afford lots of shield busters until later in the game. Some races, though -- ARs and other factoryless types -- should consider shield busters even early in the game.
The standard chaff design is: scout or frigate hull, quick-jump 5 engine, and one laser or xray. Although frigates and xrays require higher tech to build than scouts and lasers, they are often cheaper because they only require tech in one field to miniaturize, whereas the tech-0 scout and laser require tech in all fields. Chaff variations include using a better engine (the fuel mizer and rad-ram are often used) and using a better weapon (either a gatling, for sweeping, or one of the shield-sapper weapons). Generally, though, cheapest is best, since you intend for these guys to die.
Thus, if the enemy is using an all-torpedo fleet, the response is to use chaff. You should bring to a battle as much chaff as you need, knowing how many enemy torpedoes will be there, and how many rounds they will last. If the enemy has beams, you cannot use as much chaff as you might like -- beams will just slice your chaff up, since beam damage streams. Typically, though, you will still be able to use chaff for at least one round, and often two.