While keeping time with your left foot hi-hat, play eighth-notes from snare down your tom line and back. If that feels good, kick up the tempo.
i think this is a really important thing to remember, b/c i've seen a lot of drummers stop playing the hats when they go to fill or solo, and imho, it sounds flat that way. that little hat ching adds a nice flavor and states the time.
only thing i would add to the breaking up the note values thing is incorporating the bass drum into your fills. this opened a whole new dimension for me. whether you stick them in on the front, middle or back end of the fill, getting that 'womph' generally sounds and feels really good. it's hard to get the hang of, especially when you start to throw in doubles, but it's cool to hear.