Tactics

I'm a relatively new player as well, but here are the tactics I use that always makes me the big dog (so far). Btw, I play on these settings: Huge Galaxy, 7 opponents, challenging difficulty.

However these tactics work on any size map and any number of opponents:

1. Choose the Yor Collective, Federalist Government

2. Max your spending

3. Max your tax rate. Make it as high as you can and keep the approval rate above 51%

4. Follow the "Colony Rush" strategy in the beginning. There is a document on that in the Wiki area.

5. Make a 2nd generation colony ship that gets 4 speed.

6. Research Sensors first: Make a 2nd gen survey ship that gets 6 speed.

7. When not making Colony ships, make survey ships. I want at least 5 survey ships zipping around the competition while the anomalies are still plentiful.

8. Keep an eye on the military status of the other civilizations. As soon as another civ starts investing in military, you do the same. Stay on top and don't let anyone pass you. You do this by making a "Fake" defender. This is a cargo hull with some attack and defense gear. Don't waste space on engines or modules since you are making this Faker to simply keep your military score up. You will never use these ships to attack anyone.

Well, that's what works for me. Good luck.

If you're having trouble with one race dominating or another floundering, you can adjust race intelligence individually.  Set your difficulty level then take the Terrans down a peg or two to balance them.  There's also other race characteristics you can adjust under Personality.

It depends on the game, but in Dark Avatar I usually played Yor or Thalan.  In Twilight (TA), I tend to play custom race with super breeder or super hive using the Terran tree.  However, in TA, I also play a modded game where I like playing as the Torians or the Thalans.  Most of the time I go for Evil alignment, but play Neutral sometimes as well.

As far as tactics, I usually build my military fast and early then take down the other races as soon as possible.  The game is more about your military rating so even if you don't "war monger", you need to get that up high and early.  I pretty much only play military victory, but you should try all of the victory conditions if you haven't yet. 

Survey ships are key in the beginning.  If you get enough out there and build the "Eyes of the Universe" special project, they can double as both scouts and surveyors.  They'll explore all the galaxy while running hands-free in auto-survey mode.  Set anomlies to abundant in the pre-game setup.

Have fun!

After getting used to the game go for the custom race. I like to learn as many techs as posible and I follow the "Colony Rush" strategy in the beginning.

TOA, Terrans, Huge galaxy, 7 opponents and all the minor races.

Difficulty doesn't matter: higher the challenge, shorter the playtime.

Never build any starship (and by consequence no space stations): waste of resource - set the military to 0, two starting planets are good enough.

Prioritize your research toward diplomacy and influence and carve your way to diplomatic/economic egemony.

When you own 3 quarter of the galaxy choose which victory you want to see this time (Nota Bene: if you want to go for a Conquest Victory you will need now to start build some ships but it is just for to see the different ending).

In suicidal you can win in one evening (5/6Hrs), lower the difficulty longer the time to win (they are quicker at colonize and then exchange planets to your technologies).

In all the planets that you get from your opponent via technology exchanges build and regularly upgrade at least one embassy: good as influence base.

If the planet is still virgin or almost virgin go for - factory, factory, embassy, farm, multimedia center - or the equivalent. Easier to make a governor to save some clicks. Then check the bonus to choose if the planet will be a research one, a production one (no ships is fine, no possible ships a little risky), or a money one.

When you are bored to death to win every time try some less efficent strategies.

P.S. it helps to contact as many opponents as quick as possible, accept bad tech exchanges, just do a lot of them. If someone really declare war on you (instead of giving you gifts as usually appen in the end-games) just pay him off and go on.

P.P.S. Technological victory is so banally simple that the game feels brocken, best to skip it.