Here's how to lay a no-squeak subfloor. Apply a generous bead of panel adhesive to the tops of your floor joists. Lay sheets of 3/4-inch tongue-in-groove plywood, staggering the joints as you go. Use a sledgehammer against a two-by-four to drive the plywood together tightly. Secure each sheet in place with galvanized eight-penny flooring nails.
For more on flooring, consider:
Wood Flooring 101
Installing a Subfloor (VIDEO)
Enhanced Plywood and Subfloor Products