===Dangerous (but a heck of a lot more fun) way===
Breed cattle and/or horses and kill them off slowly for skill gain. You can back away from horses and cattle in order to safely bandage using cotton or rags.
Go hunting. That's it. Just go hunting. You first want to try hunting down simple farm animals such as pigs, pheasants, roosters, bulls, cows, etc. Even wild cats work at the start.