Personally, I would NOT, under most circumstances, ever abandon your home system. Waaaay to valuable, and what's the point anyways??
If you're having some trouble keeping enemy ships back, first make sure you can detect them cloaked. Then sit on the most obvious invasion route for the enemy with as many ships as you can muster. If you are guarding other warp points that haven't you haven't been attacked through in a while, move most (but not all!) of those ships to guard the vulnerable warp point. Of course, in Multiplayer games, this can be taken advantage of. Send a few small fleets through the one warp point to distract the enemy from the real invasion point, which was then weakened by your withdrawing forces from it...you get the picture.
Most of all though, the biggest advice I can give you is to try new things, innovative things, and learn. Find what works best for you, since other people's strategies may not be comfortable for you. Trust me, the process of learning and trying new things, and then having your new innovative strategy actually work are some of the most enjoyable parts of the game.

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Courage doesn't always roar. Sometimes courage is that little voice at the end of the day that says "I'll try again tomorrow".
Maturity is knowing you were an idiot in the past. Wisdom is knowing that you'll be an idiot in the future.
Download the
Nosral Confederacy (a shipset based upon the Phong) and the
Tyrellian Imperium, an organic looking shipset I created! (The Nosral are the better of the two [img]/threads/images/Graemlins/Grin.gif[/img] )