Here's just a couple of pointers for everyone, and what I've learned since starting to do covers (some tips from a non-artist such as myself that'll give your covers some pizzaz!)
1. No serif fonts. They very rarely look good and are quite old-fashioned (this goes double for bevels and any of those text auto-effects you'll get in popular photo programs.)
2. The cover image must be colourful, or have a dominant colour (this helps it stand out in amongst a lot of other covers).
3. DON'T just slap a font on top of a picture that is near to what your story is about. You took time and effort to write a novel, now take a while to come up with a nice cover (although, I don't do this at all. It usually takes me fifteen minutes for a cover because I'm like an excited child when I get an idea).
4. TEXTURE, TEXTURE, TEXTURE. Layers of paper textures and grunge textures and canvas textures all over what you're doing, then play with blends until something pops out at you and screams COVER!
5. Go symbolic. Don't try and tell your whole story on the cover. Pick out an element or two that can represent your story in a visually eye-catching way. Get a good tagline on there to entice the reader (when they look closer).
6. Do it cheap. If you're an indie you won't have the budget for photoshop or illustrator or any of that. I use all free software (both free as in money and as in freedom to tinker) such as The Gimp and Inkscape on a free operating system (UbuntU)
7. Play to your audience's expectations. If you're writing horror, grunge up your cover, a thriller, you better have something on there that'll draw in a thriller crowd and so on. Again, the big sin with covers is just slapping some text over a picture. It will GUARANTEE a large portion of your potential audience will just skip reading you.
Here's some of my recent covers (from my own publishing house) just to give you a flavour of what a non-trained person experimenting with images can come up with (all subject to drastic change).