What should I practice?

That all depends on how long you've been playing, what kind of music you like, and what you usually practice. What I like to do when I'm stuck is just pop in my earphones and listen to my playlist and try to play as much as I can from hearing it, of course that all depends on how far your ears are trained.. also, when I want to learn a song and I can't figure it out I visit this website called tabrobot.com where you can find almost every song in tablature format and learn to play it from there.. as far as writing songs go, I usually wait for the song to hit me from just messing around.. I don't force my songs out coz they usually don't come out too good.. also I revise my lyrics over and over til they feel like they come out naturally.. good luck and have fun, remember: K.I.S.S. (Keep It Simple Silly).