Experience is key. I would rather go to someone who's been a masseur for a while than someone new. Nothing against the newbies, but my knots are stubborn. He has to know what he's doing. Sometimes the reviews offer some insight.
I look for a variety of techniques in his ad, not just one. (Swedish doesn't cut it if that's all he does). The massage will be less cookie-cutter because he has many approaches to "solving the problem" areas. And like Runninchlt, I really appreciate the stretches.
Licensing is something I look for, but it may not be a deciding factor. (Isn't it a "massage" if he's licensed/certified and "body work" if he's not?) You can often tell from their website whether or not this is what he does for a living or not. I would rather it be his full time work.
I even look for those with other related services (whether it be hot stones, manscaping, yoga, personal training, etc.), since it sheds light on the person's interests. The more focused he is on "taking care of the body", the more likely there's passion for his work.