You mean racial traits? Fyron wrote a pretty good article about min/maxing your empire design available
here. The one thing I don't agree with in it is that lowering farming and refining aptitudes below 80% isn't usually worth the cost IMO. For racial tech traits, it largely depends on the player what you should take, but religious and crystalline are very powerful. In fact, religious is often Banned in multiplayer because it's TOO powerful.
For what techs to research in the game:
Weapons: early game, projectile weapons only; mid game, phased-energy weapons (requires physics 2) are excellent; late game, energy stream weapons (requires physics 1) are flat out the best straight damage dealing weapon in the game once everyone has phased shields. Also research point defense weapons (requires military science 1) to deal with anyone who might be using missiles or fighters. Special damage type weapons, like the shield depleter or ionic disperser, can also be useful.
Other combat tech: ship construction is very important - get at least level 4 fairly quickly for the large mount. Shields are good, but if you're going up against phased-polaron beams they'll be useless until level 6. As discussed earlier, sensors and combat support are crucial. High-level armor (requires chemistry 1) is also good, and allows level 1 cloaking (stealth armor) as an extra benefit. Advanced military science (requires military science 2) is important for training facilities, and also gives the cheapest to research cloak detection sensors.
Other military-oriented techs with no direct combat effect: better space yards tech can greatly decrease build times, but it's expensive to research. Repair is important if you plan to do a lot of retrofitting, and it's also a good idea to have at least one repair ship accompanying your fleets.
Economic techs: minerals extraction 2 is valuable, but hold off on 3 for a while and don't bother with 4 and above unless you REALLY have nothing better to do. Computers (requires industry 1) are quite valuable, and as a side benefit can provide immunity to alliegance subverters. Applied research 2 can give a nice boost, but don't get it too early. Troops (requires construction 1) can easily negate the penalty of taking 50% happiness (5 small troops with nothing but a cockpit on each planet will do it - more is better), allowing you to gain an extra 800 race points for other stuff without a significant penalty if you don't wait too long to research them.
Racial techs: If you took Deeply Religious, forget about sensors research; you have something much better - the Talisman. Get religious tech level 4 as soon as you can without handicapping yourself in other areas too severely. This will get you the religious talisman, which gives your ships a 100% hit rate regardless of other factors. If you think you'll have time to get it before getting into any serious wars, you can drop aggressiveness to 75% in race setup for lots of free race points with no penalty once you get the talisman.
If you took Crystalline, research crystalline technology to get crystalline armor. Lots of crystalline armor with just one or two good shield generators can render ships nearly invincible. Ignore crystalline weapons unless fighting another crystalline race, as the armor-skipping property of crystalline weapons will avoid triggering the special ability of crystalline armor.
If you took Organic Race, organic weapons are somewhat inferior to other choices for damage efficiency, but they are uniformly cheap in minerals and radioactives, which allows faster build times. Organic technology is also good for organic armor for a while, but it's real benefit is the population growth facilities. Get organic tech 6 and watch your population soar with Replicant Center III's adding 40M population to every planet every turn. Expensive, but well worth it eventually.
Psychic Race - good for alliegance subverters and system-wide training facilities, but not worth the cost IMO. Alliegance subverters can be countered by master computers, and regular training facilities are good enough for my purposes.
Temporal Race - Temporal weapons excel at taking down shields, but they cost a LOT of radioactives. It takes a lot of research, but temporal technology eventually gives temporal space yards, a 50% improvement over regular space yards at max tech. They take longer to build, though, and you can't upgrade from a regular space yard to a temporal one - you have to scrap and rebuild.
Edit: About retrofitting. Retrofitting has two uses: upgrading obsolete ships, and reducing build times. The first is obvious, the second is explained below:
Say you have a ship that takes two turns to build.
Standard approach: build ship in two turns, send to training center, wait, send to front lines.
Retrofitting approach: design another Version of the ship with only what you can build in one turn, and another with what you can add by retrofitting the one-turn-build design (calculate 50% cost difference). Build ship in one turn, send to training center, retrofit twice, wait a turn less and have the space yard build another in the mean time, send to front lines. With bigger ships that take 3, 4, or more turns to build, this approach can have the ship ready several turns earlier than it would be normally, and free up the space yard to build a lot more of them. It costs a little bit extra resources, though, but not a huge amount.