I used to play lead guitar a few bands, my approach to writing was always a bit different to the other members in the sense of which comes first, lyrics or music. As Jake said, most musicians I know write the lyrics first, but for me, it was always easier and more natural to have a riff at hand.
Back in the day, I would record my riffs on a tape recorder, but nowadays I would record directly to the computer using Sonar 4 (I recently got a copy of Pro Tools but I want to seriously upgrade my present system before I begin playing around with Pro Tools).
It is from the riff and the mood that I get my inspiration for writing the lyrics.
I never tried to infringe on the creativity of the bass player or the drummer as far as what their writing of the piece would be. Once they heard the riff and I explained to them the feel of the song, they would come up with their pieces and I may make suggestions as far as what I envisioned the piece to be like.
I would sometimes use 'Fruity Loops' to create a drum track that I may have in mind for the drummer to emulate.
Once everyone had a feel for the song, it was just a matter of rehearsing, recording and listening back to the track to see where could be improved on, tightened on etc. before a song was ready for the public to hear.