I agree with cafarmgirl.
The best start to turning away predators is a good electric fence. Don't be cheap. get one with 5 - 6 joules and plan it out so a climber can't climb around it (ie a tree with low hanging branches). Clear the ground where the wire will run, set the posts (pre-insulated step-in posts are great) run the lowest wire about 4" off the ground (not the grass) run the second about 4" above the first, run the last two strands evenly spaced with the top one at the highest spot on the posts. This will provide great deterrance for anything from possum to grizzleys.
Go tall on the fence and avoid running a top rail between posts. A shaky wire fence will deter a grey fox from climbing over. A top rail on a fence provides a perch for hawks to sit while choosing dinner or waiting for a chicken to step out from a hiding spot. If they perch on the posts, drill a hole in the top and stand a piece of heavy wire (about 6 inches) in it and that will stop every thing but a stork from
As for flying predators, it's a crapshoot. Alert aggressive roosters are great to warn the flock as long as they have cover to run to. Brushpiles, pallets on stilts, sunshade, etc make great hides as well as providing shade in the yardperching on it..
Laying the skirting on the ground with the inside edge attached to the base of the run wire (hog rings work great) will stop a digger before they can even start and it disapprears as the grass grows thru it plus you can mow right over it.
If rats are a issue in the coop, keep the feed stored in metal cans and the founts and feeders away from the coop. Also elevate the coop so they don't have a inviting dark place to live.
If snakes are a concern, loosly lay deer netting around the run, they will get tangled up in it.