hands up, i'm a lousy songwriter, but we all have to work at most things - everything from sex to fishing> Practice and fool about with a song, learn as much theory as you can stomach so then you can either forget the theory or use it- knowledge is a tool.

Or you can just pinch bits like The Beach Boys nicked Chuck Berry riffs (and so did the Beatles,Ac/Dc ,etc).

I'd start by copying some Chuck Berry licks :D

Try to believe in what you are doing, and if anyone says you ain't doin it right (even if you say that to yourself) don't beleive it.

Cheers.