Improving your vocals is a matter of practice. I always say vocals is 99% confidence and 1% talent. If you've got talent, great. If you don't, strut it.
Improving your vocal recordings, though, is another ball of wax. Rule 1 with any recording is get into the right space. Vocals are best done in as dead a location as you can find. Rule 2 is use a good mic. That means a condenser with a pop filter in your as-dead-as-possible space.
Post production, two techniques do wonders for vocals. "Doubling," or "singing it twice" as us normal folks like to call it. Sing the vocal track, then go back and sing it again on another track in as much an identical manner as you can. Play the doubled track in stereo. Does wonders to provide a rich sound.
The other bit of magic is reverb. Add just a little to the vocal mix. If you can overtly notice it, it's too much. Because you recorded in a super-dead space, you'll want to add in a little bit, but you can add in the verb in to match the rest of the mix. And play with different reverb plugins, as they are not all created equal. I have half a dozen on my rig, and am constantly looking at others.
Someday we'll win this thing...