Hi!
How do you pick your enemy?
First target: weakest & close (I go for a fast kill, usually it's a race without military, taken in 1-3 turns with some single weapon fast cargo ships and troop transports). If there are other non-militarized AIs, I go after them next.
Next targets:
- If I'm strong enough, I attack the closest bully (ususally Drengin, Korath or Yor).
- If I'm not, I incite war among bulies and after they lose some military, attack the losing side.
- If I can't incite war among them, I try to incite war with bully and my strong neighbour, and attack him after he loses some military.
In any case I go for a quick kill - the war shouldn't last more than 5 turns, else I risk surrender to some other civ, or "war has expanded" event. This approach takes serious preparations: gatering info on target, placing econ starbases to extend range (and lately support production), counter-designing his ships, placing proper amount of troop transports and ships to his border and rear area. When I actually attack, I go for his planets, not fleets. This way he still has good military score, and doesn't surrender too fast, despite losing a half of his empire in one turn.
BR, Iztok