I kinda play different, but its up to the sound really man, Heres one of my sone layouts:
Intro-
Riff 1,
Riff 1 follow up,
Riff 1- riff 2,
Riff 2
Riff 2 follow up,
Riff 2-riff 1,
Chorus,
Solo,
Chorus,
Riff 3,
Riff 1,
Riff 1-2,
Riff 2-1,
Riff 3-2-1,
Intro,
Chrous.
I dont sit down and write music by scales and bars. I remember the most part and do tabs for the lyrics. Everything else i match together according to how it sounds, not any type of pattern.
Metallica's Saint Anger album is a good method for learning song writeing and how to put riffs together. IMO.