(I love this answer...) It depends.
Unless you have a dog that you are going to enter into dog shows, it doesn't matter. In a dog show, you always walk your dog counter clock-wise around the judge. Because of this, it is best to teach your dog to walk on your left side. This will keep your dog on the side of you where the judge can observe and grade.
If you don't plan to have your dog entered into dog shows, it doesn't matter what side of you your dog walks. With that said, let me give you some pointers regarding walking:
- Pick a side that you want to walk your dog. Left or right, it doesn't make a difference. The important thing is that he is always walked on that side. This helps to build his perception of "where he should be" on a walk.
- If you have a "big dog", pick the side where you and the rest of the "walkers" have the most strength. If you need to correct him, it is important that you do it from your strong side. (i.e. Are your left handed or right handed?)
- Everyone must walk him on the side that all of you have picked. If you don't do this, it will add to his confusion and extension of the learning process.
- Make sure that he walks next to you and not in front of you.
- (My pet complaint!) Use a regular six foot leash when walking. NO EXTENSION LEASHES!