I most certainly do NOT use Greek-style yogurt when dressing fruit salads. For that I simply grab a thingie of Yoplait Key Lime yogurt and stir it in with the fruit.
(And yes, I know, "I simply grab a thingie" does have euphamistic overtones. Live with it.)
I haven't actually tried any of the Greek-style yogurts that are on the market now. I've certainly had plenty of them pass over my scanner lately. However, whenever I've made a batch of tzatziki, I've started by making a yogurt "cheese," which is simple enough to do.
Oh, you want to know how. OK.
Start with a container of plain yogurt. Don't bother with those flavored kinds, they simply won't do. I usually get a large container, about two cups or so. Line a sieve with cheesecloth, or even good paper towels will do, balance the sieve over a bowl, and dump the whole container of yogurt into the sieve. Wait a sec, that's not what I mean. Take the yogurt out of the container, and dump the yogurt into the sieve. The plastic of the container won't drain too well. And then just let it sit for 45 minutes, or an hour, you don't have to be too picky about how long, you just want to let the whey of the yogurt drain out. The more solid yogurt that is left in the sieve is your yogurt cheese, which you can put right back in the container, no need to waste good plastic.