from Washington State!
Also, be sure to look at the coop designs section at the top. Use hardware cloth to keep predators out (chicken wire won't) and make sure you bury your wire or apron it out (search here for hardware cloth apron) above ground to keep digging predators out.
This is for a predator proof run. If you are only interested in predator-proofing your coop, then that's different. Some people have a not-so-predator proof run and close them up tight each night. That's cheaper.
But sometimes dogs and raccoons can come around during the day. And hawks from above. Netting overhead is great but take care to build it for a snow load if you'll have it. Netting is sold heavyweight if you need it.
Minimum run size is 10 square feet per chicken, and 4 square feet in the coop, as stated above. But I agree with the above poster- they are definitely happier with more run space if you can do it.
Remember that when you order female chicks, it is only 90% accurate. So if you order 100 chicks, it would not be unusual to get 10 roosters.
I have ordered from McMurray Hatchery and MyPetChicken.com, and been pleased. But I don't have Leghorns. Some people like Ideal Hatchery and ...hmm...you can do a search for "favorite hatchery" or something like that - I have seen threads on that.