As for beam, a lot of girls think that because they're already high up off the ground, they really don't need to add more height to their dismount. However, that is very far from the truth! The higher your dismount, the better! The judges like it better, it looks better, and it will be easier to stick your landing, so definitely make sure you're setting nice and high. You don't want too much forward lean upon take off because it will add too much distance and take away height, which will make landing pretty difficult. Stand up nice and tall with your feet directly underneath you when you punch!
As for floor, it's the same concept, you just need a bit more power (speed) and you'll need to block more. This means that instead of having your feet directly under you like during your punch off beam, your feet should be slightly in front of you instead. This will provide you with more height.
A solid rule to go by is that landings that are nice and high are easier to stick because you "drop into" your landing and all your momentum is going down into the mat. Conversely, landings that have a lot of distance usually have excessive rotation too, and are way harder to control, so you'll likely have to take a step or two to control the extra momentum.
If you are willing to provide a video I'm sure we could all help you substantially more, too.