I have to be honest, I heavily modify the game using RebEd. I dont like how default it takes forever..and I mean forever to build a ship. I also modify the hyperspace travel time for ships so I am not waiting 100 days for a ship to arrive somewhere. With that said, I usually use one fleet per sector. Any extra fleets I make I try to use to hunt the rebels. (typically I play as the empire). I also tend to invest heavily in anti-starfighter ships since as the empire I find out that the rebels can kick arse with their fighters..at least till you start getting interceptors and defenders. Carracks are your friend till you get Lancers and better fighters. Nothing more aggravating than seeing a Star Destroyer get destroyed by 2 x-wings..heh.