When first starting, keep attacking and do not allow your opponent time to recover. Focus on the weakest forces, then work your way through the rest of the fleet. Although you may lose some of your fleet, you can rebuild. Tap the "Max Power" icon when you start, then begin attacking. The better you do, the more stars you will earn, and the more you will be able to unlock later. Attack as many ships as possible to gain experience and reputation. This will also allow you to gain resources to strengthen your ships, and as well as the chance to capture extra ships.