Also, if you're not using them for crafting, auction off some particle traces. I just netted a quick 250k for a starving LtC by selling a single trace. (Yes, I know, you can also donate those to the fleet crafting group.)
I always thought I was doing OK for energy credits, too, until I saw the amounts being spent at this year's Pride auction. Usually I've been winding up my VA's with 2-4 million, but apparently that's chump change compared to my fleetmates. :)
I guess the financial side of things is a whole other mini-game within the game. Sometimes I get bored with going back to starbase when my inventory fills up, and I don't get top dollar for my goodies. Other times I spend so much time at the auction house it seems I don't get to play. There must be a happy medium somewhere.
If you have multiple alts, one thing you can do is make sure you start a bunch of auctions from one toon before you take a break from that toon. The auctions will work themselves out while you're playing another toon, and then when you check back in with the first toon, you may already be rich!
I'm looking forward to hearing others' suggestions, so I can buy me a fleet officer next year! But which one? They're all so adorable! ;)