Keep toes pointed at all times. This is very important for the visual appeal of the jump. Do not reach for the toes in jumps. If you touch the toes, it may stop the jump from achieving the hyper-extended position. Instead, reach for the inside of the shoe.
Many judges rather see great form over height with bad form.
Keep that in mind when practicing. Landing seems to be one part of jumping that people do not put a lot of emphasis on. However, landing is a very important part of the jump. Without a great landing, the whole jump can look awful. Whip legs shut when coming down from a jump.