Cody was pretty much a natural at walks. As far as we know, he was never put on a leash before we got him, but at 8 weeks, we put him on a leash (just a collar, not a harness) and away we went. I think it helped that we used the leash on him a lot for other things too. The first thing he did with us was a 2 hour trip home, so we made frequent stops and brought him out in the grass on a leash since we didn't know when he had last eaten. We also have two leashes that we hook up together and tie to a pole outside when we're home but can't be with him (or he's refused to go potty for the last four hours and we're sick of standing around waiting for him so we can bring him back inside
)
as for the treats, he won't touch carrots (we tried to use them for fiber), haven't tried apple, won't touch strawberries (also tried for fiber) but he does seem to like Iams puppy biscuits. Sometimes he's stubborn and won't touch them, but we make a big deal about giving them to him because they're a potty training praise- we just break off a bite size piece so he gets about one full biscuit a day but at lots of different times. He's usually pretty excited about them though