OK, so it's not really a strategy specific to TA or DA, but I thought I would describe a classic tactic which might be helpful for n00bs.
Building Military Starbases
If you're outnumbered and outgunned, you can't beat a well placed military starbase to tip a war in your favour. It's also very useful if the war is going on on the other side of the galaxy.
The tactic is simple: take any race you are at war with, pick a good spot near one of their main planets and send a few constructors. The trick is to send the constructors as a fleet of at least three, so that when you come to construct, you can fortify the base before the enemy have a chance to blow it to pieces. You then need to send a few more constructors to the base to beef it up. The amount of beefing up depends on how outgunned you are.
Send an escort of ships with the constructors. This fleet will become your starbase's defence fleet and will never leave the starbase's areo of effect. It's useful to make these ships pretty quick. These ships will become pretty damn tough once your constructors get fitted with ship assist modules, and a sinlge fleet should be able to take on any enemies that enter the starbase's area of effect. The AI will invariably aim for the starbase, rather than your ships (which makes sense, as your ships suddenly become vulnerable if the starbase is destroyed). Your fleet needs to stop any enemies from reaching the starbase.
This starbase becomes your base of operations. I always set fleet rally points to right next to the starbase, and set all my planets to send ships to this rally point as they are built, so I then get a steady stream of ships there. Because I always play Gigantic or Immense size maps, this is essential, as it can take 20-30 turns to get a ship to the other side of the galaxy where the war is being fought.
Once I get enough ships for a fleet, I send the fleet into enemy territory to start attacking ships and generally causing a nuisance. It's useful for keeping the enemy's military down. Then it's a question of sending a few transports and taking the enemy planets. Send the transports to a spot nex to the starbase, where they can be guarded until it's time to strike. There's nothing more annoying than losing a fully loaded transport that gets destroyed because it's forced to sit next to a planet that it can't invade.
Where you place the starbase depends on what purpose it serves. If your ships are not strong enough to take on the enemy, then you're going to have to place the starbase close enough to cover an enemy planet. This is risky, but it's the only way you're going to take on the enemy. Expect to lose a few starbases.
If you're looking to start a base of operations, then place the starbase just outside their area of influence. They're less likely to bother you there, giving you time to set up a nice base.
The downside of this tactic is that it's expensive, and your starbases become pretty much obsolete once you've taken the enemy planets near them. Only use this strategy if you really need to.
