Many market stalls here let you try at least a segment of one before you buy. Small tangerine types, you'll usually get a whole one. Of course, it isn't a 100% guarantee that what you buy will be the same, but usually near enough.
Very seldom do you get to try in supermarkets, though. I find sniffing them is a good, if not foolproof plan. The good ones usually smell better, too.