Build Construction Yards. Get one or two planets filled up with nothing but Construction Yards. Build SYs, and Barracks, get the planets filled up with nothing but SYs, and Barracks. After you've done this, let the droid automanage your resources, and just build up your fleet from there. Oh, also recruit as many people as possible, and assign as many as you can to research.
Heh, I remember one glorious game where I had a Death Star blow up one planet, only to have 10 more join the side of the Rebels. And then there was the time I had an awesome fleet of three Executors, six ISDs, ten Escort Carriers, and craploads of TIE Defenders.