- practise them on a daily basis
- play with a metronome
- practise to play them straight on your max. speed for a few minutes (if you can not, you play beyond your actuall max speed! - slow down a bit)
- practise to play them from slow to fast
- have patience
- do not push anything
- use a technique which does not require triggers (!)
- look on youtube or such to get fimiliar with some techniques and use the one you are most comfortable with
- play relaxed (!!!!)
Considering this points ... do never ever let them take over your practise time!
Playing a good and fast blast does not make you a good drummer. Work on other things as well (even if you don't think you will ever need them).
Try drummer and/or metal forums for further informations.
Regards