Hello Raven and welcome to the site.
I will give you the same advice I give every newbie…..lol.
Read the manual cover to cover, and go out and get yourself a Bluecrane digital video on the D90. Taking great photos starts with knowing what your camera can do, or better still, what you can do with your camera. Then just get out there and shoot anything and everything. That’s the beauty of digital; you can shoot to your hearts content.