AirForce_Guy... Welcome to the forum and modeling in general!!
I'm not sure what your technique is, so here are some general thoughts and ideas:
1. Try using a low tack tape. 3M's blue painter's tape is very good.
2. Try using a thinner tape. I have used Scotch tape with very good results. When the edge is burnished well, it gives some very exact demarcation lines.
3. Don't spray thick coats on your model.
4. When spraying, don't spray INTO the mask. Angle your airbrush so that you are spraying AWAY from the mask. You'll avoid paint build-up along the mask edge that way.
5. When removing the tape, pull the tape AWAY from the painted edge. Don't pull straight up. Instead, pull straight OUT.
6. Make sure you have allowed the paint to set up properly prior to removing the mask. Also ensure you have a good primer base.
7. As a last resort, take a new #11 blade and run it LIGHTLY down the mask edge to cut the paint from the tape.
8. There's a good article in FSM on using Silly Putty as a masking medium. You might want to experiment with it.
One final thought: Before using any of these methods, go down to your hobby shop and purchase a pack of sheet styrene-or just use an old model. Practice some masking and spraying techniques on them, and find out what works for you personally. Then go spray your pride and joy! Hope this helps.
Gip Winecoff