I just got that same model a few months ago. Had a thread going, and some members gave me some good info about micro lenses.
I'm saving up for the 105mm f2.8 micro/nikkor lens right now.

In the meantime, if you're using the 18-55mm kit lens, just get a tight a shot as possible. Then enlarge it on the pc. With the high resolution, you can blow it up a bit w/o any pix-elation.