Steve, you can learn a lot by singing with other people. Find singarounds that emphasize chorus song, and then sing along. Make sure your voice matches the voice of the person next to you (and try to position yourself next to the good singers). Don't sing louder than the people around you - the object is to lock your voice to theirs so that you sing as one voice. And when you're able to "lock" with others like that, it's one of the most wonderful things you can experience. And you'll become a better singer very quickly.
-Joe-