Appropriate fencing and a secure coop are the best way to protect your birds from predators. Depending on what kinds of critters you have in your area, you may want to keep in mind that traditional 'chicken wire' is actually large enough for a raccoon to reach through and grab a chicken's head or leg, so you may want a smaller weave hardware cloth or welded wire. If you have a lot of hawks, eagles or owls in your area, you may want to consider an awning or poultry netting to cover your chicken run.
If you choose to free range your birds, be aware that you will likely lose a few to predators. We free range our birds and have been fortunate enough not to lose any chickens; however, our guinea fowl roam a bit further and we've lost one to hawk and one to what we think was a possum. Personally, our greatest defense against predators is our livestock guardian dog. We got him to keep the coyotes away from goats, but he has proved to be a great defender of our birds as well. Just a few days ago, even penned in with the goats, he sounded the alarm to let us know a skunk was trying to get into the coop. When we came out with the gun, he was pacing around trying to figure out how to jump the goat fence and take care of the problem himself. Obviously, not all dogs are fit chicken guardians, but many breeds can been effectively trained to guard chickens. Our dog is a Great Pyrenees/ Anatolian Shepherd mix - both these breeds can be trained to work with chickens. If you want something smaller, I've heard Corgies are a pretty good choice.
golden feather seems to know the answer to alot of your chicken questions , don,t be afraid to ask any question , it just might save your chickens life , people like golden feather and i have been doing this along time , we have probably got the answer to your question or your problem . god bless . wv leipers