Here's what i do for snare gating. gotta give credit to milar for this one...
Other than all the thins you guys have already mentioned ,
I take a copy of the triggered snare or kick , shift it back 10ms and send it to the side chain input of the gate on the kick and snare mic track. Gate only opens on actual hits, and opens a little before to stop the transient getting fucked with.
Mint