Get one of these:
Nikon Normal AF Nikkor 50mm f/1.8D Autofocus Lens 2137 B&H Photo for low light, high speed, depth of field and amazing sharpness.
Learn how to do the proverbial "foot zoom".
Shoot closer to the subject than you think.
Don't perfectly frame everything.
Learn depth of field and relation to f stop.
Most lenses shoot their sharpest somewhere in the middle of their f range.
Most post processing software is better than in camera.
Shoot, shoot, shoot.
Have fun.......