How much to buy in for in NLHE?

I'm trying to decide the best amount to buy in for in NLHE. I mostly play 1/2 and 2/5, where a full buy-in would be $200 and $500 respectively. Many books suggest that you should buy in for the maximum so that if you get a chance to break a big stack at the table you won't be short-stacked against him. This seems like good advice. However, much of the time that all my chips go in I've only got about a 10% advantage, which I don't like because I'm risking so much money on such a small edge. Sure, its great when you've got the nuts against the second nuts, but much of the time I don't have that much of a lead. Lately I've been buying in for the max at tight table where it is more likely I will get into a big hand vs. big hand scenario. At loose table I've been buying in for half of a full buy in to minimize my losses on hands with small edges. Barry Greenstein suggests that you usually buy in for the minimum in his book (if I'm remembering correctly). How do you guys and gals decide on your buy in for a particular game? Is my thinking totally wrong on this? Bear in mind that I'm not a pro, but I do keep a separate bankroll that I like to build upon.