Don't know what you should write? Read! Reading always helps to get inspiration! Whenever I can't figure out what to write, or what one of my characters should say in one scene I read a few scenes from my favorite books.
That usually helps me get in the 'writing mood.'
Also Googling certain things to help me figure out what to say (write) helps too. I had a small case of Writer's Block the other day and this helped a ton!
Check it out,
What Makes a Good Story?