I usually write my music on a piano, and I really enjoy performing that way, because that actually shows how the music was in my mind before it actually became an electronic song.
The process is always the same. I get an inspiration for a new song, I put it down on paper immediately so I won't lose it. When I am ready to go to the studio with it, I play it a few times on the piano and edit, add, and type the lyrics and take it to the studio. Sometimes I don't have anything on paper.