What Herb said will help a lot. There should be some pretty good warm-ups for singing posted somewhere. Since I only do voice-overs, I tend to only use one exercise called the "King Kong" warm-up. For that one you simply say the following starting in a fairly low register (and varying the order on subsequent repeats): "King Kong," (then lower) "Bing Bong," (then even lower) "Ding Dong." On the final word of each set (in the case shown, "Dong") lengthen the word and stretch it lower and lower until it becomes unrecognizable. Think of this as if you're stretching a muscle gradually. The next set you should find you can go a little lower, and so on.
This exercise naturally helps with the lower tones and a bit with projection but, I'm sure, that the singing ones will help with your breathing and where you're supposed to sing from (body part-wise - a singing coach can describe this area a lot better than I can! LOL!).