1) use a good deck screw, not drywall screws, they might bust heads with any foundation shifting and cause MORE squeaks. Plan on 2/3 of the screw going into the floor joists. Spacing every 10 inches, counter sink a bit also.
2) lay the ply wood like the first two courses of laying shingles. ie, lay a complete sheet first, then on the second run, a half sheet. This way the intersection lines DO NOT line up, but staggered.
3) some thought on this question, but I would butt up all the sheets, except for around the walls, here i would leave a 1/4 inch gap for expansion and movements.
I am not sure about the glue on the floor joists lets hear from others, I would not use it and rely on the screws.