nereo hit it on the head. If you're a junior or senior, you get $7500 (minus the convenient 1.04% origination fee) that'll cost somewhere near 6%. The difference between subsidized and non-subsidized is only whether the government pays interest until 6 months after you graduate or if it accrues from day 1 and you get to pay it.
With a cosigner, there may be private loans that have lower rates. Without a cosigner, I'll state that there simply are none.
Filling out FAFSA is the first step. Without it, you get no government aid (loans, grants, work-study).