Fall to your knees in prayer and ask the Almighty to nudge the devs in the direction of giving you (and more importantly, me) a real player's manual. Yes, the menu on the front page of this site boasts a manual. It is as useful to us as Joe Biden has been to the President.
Failing that, fall to your knees and give thanks. You're about to play one awesome game.
1. Don't worry about energy credits. Yes, at the start you'll wonder how you're ever going to get in to the hundreds of thousands, but trust me, by the time you hit Lieutenant Commander you'll be doing mighty well for yourself.
2. Sell, sell, sell. Honestly, if you're not going to use that new shield array you picked up, sell it. don't hoard it. This ties in to point one.
3. Don't feel restricted. If you want to be a science officer in a cruiser or something, then do it.
There are others, but those are the main ones i think.
1. Get through all the podcasts from Priority One and STOked aswell as Tune into Subspace-radio.net
2. Don't be afraid to ask anyone for advice on sugestions for your builds and playstyles or general mission help.
3. Have Fun