Directly contacting a referee of my paper A few months ago, I submitted a paper to a journal, and received a "can be published if such-and-such issues are addressed properly". I know who one of the reviewers (the one that wrote the most helpful review, in fact) is, largely because he decided to reveal his name in the review. In a couple of weeks, I'll happen to be in the vicinity of his university (this is serendipitous; I had already planned this trip before I knew he would be one of the reviewers). 

Is it acceptable to contact him, tell him I'm the author of that paper he reviewed, and ask him if he has time for a meeting to discuss how I am addressing his comments? I have no shame in admitting that I am considering doing this to ensure that he is happy with my amendments to the paper, which in turn should make the second round of reviewing go more smoothly.
This should depend on the journal policy. Both you as an author and the reviewer are bound by the rules the journal has in place with respect to the publication process. While it sounds like you are meeting with the reviewer solely for the purpose of improving the paper but it may come across as going out of one's way to others. To be on the safe side, I would suggest you contact the journal editor before organizing such a meeting. With a sign-off from the editor, you can be sure that you are playing a fair game. I would also keep co-authors in the loop if any.