http://www.sr20-forum.com/suspension/1801-b13-b14-b15-suspension-information.html#post24096
Unsprung weight - Consists of anything not supported by the springs. Your tires, wheels, and brakes make up the majority of unsprung weight. You want to minimize unsprung weight.
I could be mistaken, but the answer to your question is pretty self-explanatory.
Question: If your
tires, wheels and brakes make the majority of unsprung weight, what would a person do to minimized unsprung weight?
Answer: Buy lighter tires, wheels, and brakes.