How do I stop him from biting me?

I started working as a dog walker back in August and there's one particular dog i've been having problems with.
He's really well behaved most of the time but there are times when he'll start jumping on me and biting my arms. He does this for two reasons- mostly when I'm playing with him and he gets a bit excited and sometimes when I put him on his leash and he wants to get off.
When he started doing this i'd say 'No biting' and if he stopped I'd give him a treat or rub his belly and when he didn't, I'd put him on his lease (he hated being on his lease in the park). He's a collie, so he loves to run around, so if he kept it up once he was on the lease, i'd hold him by his collar and make him stay in the one spot for 2 minutes.
This worked really well, but he has started again recently. Putting him on the lease doesn't work anymore though as he has matured alot since and doesnt mind being on it anymore.
I use a water spray for the same problem with a puppy I look after, but I really doubt a spray of water would work with this dog.
A few people have suggested hitting or kicking him when he does it to show him that he's hurting me.. I've done this once when he really hurt me and I needed to get him off me asap, but I hated doing it to him and I wouldn't have the heart to do it to him any other time.. Besides, kicking him didnt help me at all at that point.
Any other suggestions?

- Redirect. When he bites, shove a toy in his mouth and praise.

- Remove yourself from the situation. When he is biting, get up and exit the room. Eventually he will understand that when he bites you, playtime ends, and that sucks, so he better control himself. :)

- Be consistent. Pick a method and stick with it... don't do a million different things. It's only going to confuse him. Results will probably not appear overnight. Lots of patience required with a puppy.

Your right I wouldn't want to hit/kick him either, it dosen't work anyway. Try turning ur back on him when he bites, this will make him feel excluded from the pack. also make a loud sound just before he goes to bite. hope this helps.