My skimmer overflowed on me, once, when I was feeding corals. Here's what I do now:
1) Unplug my return pump
2) Break the siphon so that my sump doesn't get anymore water than the return would allow (my sump wouldn't overflow as there is a 'failsafe' sump break pinhole in the return head in the tank, but when I didn't do that, my skimmer overflowed then as well)
3) I leave the skimmer on
4) Turn off my MP40's
5) Feed coral - let sit for roughly 15 minutes, until food is either taken, fallen down, or suspended.
6) Turn on MP40's for about another 10 minutes
7) Turn back on return flow
Watch skimmer as return flow evens out, to make sure it doesn't overflow.
Since I've used this, I haven't had any problems. From what I'm told, the oils in those foods can get into the pump/skimmer and cause it to overflow.