Flat out is fine... it's usually when you gap out your friends and then don't give them a chance to catch back on when people get upset... especially boys.

On technical descents, you will probably trade ultimate speed for smoother corners, building up your entry and exit comfort and speeds. Remember to weight your outside pedal, DO NOT worry about pedaling through corners (It means your center of gravity is very high if you do), exhale before the corner and bend your elbows. Your head shouldn't be to the inside of your stem (if you were to draw an imaginary line from the center line of the bike) either... but we could talk all night about cornering!!

Most importantly, Have FUN!!!