There are two ways to do this - decrease your BF% and improve muscle separation. Diet is the way to decrease BF%. As for muscle separation - you need to do exercises that utilize as many of the fibers in your quads as possible AND at full range of motion. That means deep squats and full hip extension at the top of the rep. Go heavier and explode up from the squat to the top to activate those fibers. It might also help to do tabata squats:
Thanks for the info guys, cleaning up the diet helped a bit and limiting amount of milk intake. Also found that following up squat or deadlift day with sets of 20 (or more) with leg press or squat fired up the quads.