I have no idea what the law is about traps where you are, here you are required to check them twice a day. Which is a bummer because you spread your scent all over. And the last thing you need is to be reported by an animal rights type.
The best luck I've had is to find the dens. Map them and visit periodically to see which are occupied. Set up a quarter-mile away. The reason being it has been my experience older Fox are smart, natural selection the young and stupid die first. The smart and alert ones know when you are closer than a quarter of a mile. You set up and hope they make a mistake. Fox are rare in Yote country. Dens are usually (but not always) where the soil drains well. If you go walking with your Dog he will find them a lot faster than you will. For Yotes I look for scat, for Fox I look for dens. Check out the fence lines, Fox and yotes favor some kind of cover in daylight, and fence lines are sometimes the only cover around. I've seen beaten paths right along a fence line where the Fox are traveling to and from the Den. Open stubble fields are for night hunting. When the grass is wet they favor hunting the ditches by the farm roads. They will, but they prefer not, to get soaking wet. If there are hay rolls around check them out, they often turn them into Fox hotels. They are also partial to culverts and drainage pipes. Check out the season for Fox, Yotes are usually all year.