We have our entire yard fenced so nothing can get in, except the neighbors Doberman who jumps right over. For him we call the pound and if we complain one more time they will fine the owners and possibly confiscate the dog. if I ever catch him near my chicks it's my legal right to shoot him, but the fence has been absolutely successful against all other dogs so far. We paid the extra money to make sure we got a fencing type that keeps even small dogs out. Our chihuahuas can't even get through, and we were careful with gaps between the gate and posts. The chickens should not be able to fly over it or perch on it. We were careful to make sure there were not diagonal planks at the top of the fence for them to perch on. The neighbors barn cat we let be because she is around chickens elsewhere. Otherwise we would trap them and take them to the pound(honey buns work best for trapping cats, skunks, etc) and any other small animal(possums, raccoons, etc) would get the same if they became a problem. We lock our birds up at night in a raised coop so nothing can dig into it.
Besides dogs, hawks have been out biggest problem. Roof your coop with a reflective metal, hang reflective objects/etc to confuse hawks and impair their vision. Tie twine with ribbon ties across the top of the chicken run to keep hawks out or have a covered run. Avoid white poultry breeds as they are easier for hawks to spot. Keep injured, etc birds in a covered area until better. Predators will often pick them off first.
My chicks get full access to a covered yard and supervised runs in a larger yard. I won't let them completely free range the whole yard(fenced to keep dogs out and chicks in) until they are big. Still, I will probably lose several to predators once they have complete freedom of the yard. I can't protect them completely unfortunately.