Just a note about humane traps since you've never used one before...
Once the cat is trapped, watch your hands! We had two litters (1 year apart) under our shed in our backyard from a stray. We trapped all the kittens and had them spayed/shots/etc. The type of humane trap we used was mesh on the outside instead of solid (I know they make both), but we chose this one so the cats could see the food as well as smell it. While some ferals just get nervous and hide in a corner when trapped, some come out fighting and will climb the sides of the cage to get to your fingers... so if youre not careful when you pick up the trap, you'll have the same scars as if you caught the kitten with your bare hands
So... just a thought... gloves might be a good idea when you pick up the trap for the first time with the kitten in it or your hands may end up looking like mine
As for bait... I agree with Hissy that sardines and smelly fish work best, but if the kitten seems not to like fish (some of mine dont.... go figure
) we caught a lot of our ferals with hot dogs as bait.