If you can get ahold of a snare, try setting it around the hole it's been using to get in your coop. If you want to try live trapping, the trap needs to be fairly large. Yes, bobcats can get into small holes, but they're usually going in for something alive. Remember, they are very skilled predators, to live bait always works best. IF you cannot or will not use live bait, try sardines, tuna, or even fresh chicken. Camoflague the trap as best you can to make it look natural. A foothold is your best bet- if you're going to go that way, you need to be sure to get one strong enough to hold it. You'll need AT LEAST a #3 double underspring, but I reccomend a #3 or #4 double longspring. If you use anything less, chances are it'll pull it's paw right out.
*DISCLAMER* For my own sake to avoid flaming and hate mail, always check your local laws before taking action*
Whew! That being said- I will always get rid of predators if they are causing problems.