It may take a few days (have patience) to determine if mom cat has more kitens, or just the one that you saw. I have most luck catching them either very early in the morning (I rarely go trapping at 6AM ) or just as it's starting to get dark. You should really put food down for a few days to see how many you're dealing with, before setting about trapping them. Leslie and I did a trapping job some years back that entailed crawling around under a trailor (fun with the rocks under there..ughh) and checking inside every cinderblock hole. We scruffed, and grabbed up (6?) tiny kittens, and then got the mom cat. I got a call the next day that one more kitten was heard screaming from the marsh reeds the next morning! So it is crucial to determine the number of kittens first. If you have access to a large trap, tie it open for a few days, and put plenty of wet food at the far end. When the cat and kitten(s) are going in without hesitation, use a length of rope to control the door. Be sure the trap doesn't move as your holding open the door. Brace it against something, but not so you can't tell if they're all in yet. Sit in your car a distance back, and when all the cats are eating from the far end of the door, let the rope go, and cover the trap completely with a sheet, or blanket to calm them. Have a flashlight on hand to make sure no kitten butts are sticking out of the trap before you let the rope go. This can be time consuming, but it's a great way to get the whole family at once! Put enough wet food into the dish past the trigger in case one goes in and backs out. Smoosh the food up also so mom cat doesn't grab a mouthful and take it to the kittens. I use car mats for the trap bottom (Walmart carries small ones) that can be bleached, and don't shift in the trap due to the nubs on the bottom. They sell grey ones for $2.00 around here, made for the backseat of cars. Cut to fit trap. Be sure if you are borrowing a trap, that it doesn't smell of other animals. Clean it with a bleach solution first. Then there's the next dilemma that Donna brought up...what if they're feral? Any age guess on the kitten seen?