Help on teaching myself how to sing?

I'm 17, and people say i talk in a monotone. I'm very musical, i'm musically inclined, i play trumpet, the drums, i played a little bit of b and i'm learning guitar. I want to teach myself to learn how to sing well, i'd say my range is around a tenor or alto. I'd say my voice is somewhat dry when i do sing, i can try to sing songs like Everlong by the foo fighters, or sort of low voice areas. like Julian Casablancas also. I could sing some of the things Dave Grohl sings by taking it down an octave. so yeah. Are there any tips i can have? I don't smoke or drink or anything. If it helps, my goal by the time i graduate (2012) i want to record an album, by the end of this summer i want to record at least a demo and i write all the music i'm going to record. I just need help on teaching myself how to sing because i wanna sing well especially for my demo.