I shower about every other day. I know when I need to clean myself, its like a spidey sense.
If you brush your hair properly then you don't need to wash it every day. Its really unhealthy. If you brush the oils from the top of your head to the tips of your hair you'll be fine. Because I have curly thick hair that gets dry easily, I wash my hair twice a week and condition it just the same.
Its always nice to put on some nice lotion after a shower as well.