Ranger had his done in December and now has most of his freedom back. Look for a physical therapist. We used one for Range and so far the return to normal activity has been a smooth one. Take pictures of the leg from the get go, that can help document the progress, we used video too once he started out on short walks.
Our vet gave us a little different advice than others here have mentioned, he had us taking him out for short walks fairly soon after surgery, be sure to ask lots of questions or even better write up a list of questions, if your like me, you'll forget half of them. Find out if the vet will answer emails, ours was very good about this.
As for keeping him busy, there are puzzles you can try, we gave him beef knuckle bones occasionally and worked on focus.