The way I play it in a ring game..

On the flop, 75% to 100% of pot if I've got top pair nice kicker.

Now, if somebody is calling this huge bet, I'm about 98% sure he has a flush/straight draw or top pair, nice kicker (possibly nicer than mine). If he originally checked to me and now he is calling, I'm 100% sure he has flush or straight draw.

Flush/straight draw completed on the turn or river, I'm checking. If its a small bet to me, I'll call. Otherwise, I'll fold. I don't think its worth it to put down a small bet. I used to put down a feeler bet, but on party poker, a lot people play anything suited, and I've just got burned too many times by it.

Also, in the not-that-rare situation where a weak player called your flop bet with a weak hand like two overcards or Ax, I've found that these players are so weak that they won't capitalize on the fact that you're showing weakness by checking after the scare card comes down. They are happy just to check their way to a showdown.