Sticky traps actually work great for snakes small enough, they get so stuck they arent able to do much harm to themselves, and a little bit of vegetable oils is all thats needed to get them off. They can be dangerous though because anything that touches it will get stuck so it must be checked a few times a day. A cheap way to make large traps is to get a big plank of wood and wrap duct tape with the sticky side out around it. The black tark also works great, but it does so because the snakes feel comfortable and want to hide under it, and I have a feeling attracting snakes is not what you want to do. You can also catch them by making a minnow trap of sorts, late a 2 liter bottle and cut the top off where it starts to narrow, put it back together inside out so the opening is on the inside. Its easy to get in but nearly impossible to get out. Snakes follow walls or fencelines, they do not like being out in the open, which means they are vulnerable to predators. Any trap you make put at a corner or alongside a wall. Ratsnakes are probably the most common your going to deal with, and if given the choice they will climb so keep that in mind when setting traps or snakeproofind a place.
Another way to at least find out what is comming in and where its getting in is if you lock everything up at night, sprinkle some flour around the perimeter a few inches wide when you know its not going to rain or anything. Not always does it work but once in awhile you will be able to tell whats leaving tracks and where its sneaking in.
