Creating good warmup exercises can be a tricky task. The basic aim with any warmup should be to prepare both the limbs and the mind for the upcoming gig/recording/practice session, and for this reason I try to avoid doing anything too mentally or physically taxing, whilst also steering clear of anything mindless. The exercise below is designed to get the hands warm whilst also requiring just enough co-ordination to limber up our musical minds.
Below are 4 Paradiddle inversions with a permutating accented flam moving through each beat. Next time you sit down at the kit, try working through this exercise for around 5 minutes and see how you feel.