The best is the sqaut. But machines and leg presses will not sufuce, you MUST do a fre weight squat with a bar across your shoulders. Add a litle weight, youd be surprised what you can do!
go down until thighs are paralel with floor. Your glutes should cane the next day!
i you want to build strength but not bulk, try doing 30 reps (with a weight that makes the 30th rep burn).
other wise do 10 reps (with a weight that makes the 10th rep difficult)