I can't do it. Can you? How do you go about doing this?

I often see people playing a hand, and somehow they "know" that their opponent is on a strait/flush draw, or overcards, or perhaps an overpair. I've been trying to read players, but I'm having trouble with the limited information available in Texas Hold 'Em. All I can observe is starting hand selection on the occasion that a hand is shown down. I play Sit 'N Gos, and with the aggresive style that is typical of the lower stake games, many pots are won uncontested. I suppose I need more information than that, but I'm not exactly sure what to look for, and how to make use of the info.

I guess what I'm asking for is critera to use when trying to read a player, and how to apply that information. I'm sure many of you are going to tell me that it just takes practice, experience, or instinct, and I'm trying my best to learn, but I don't think I'm going about this the right way. I find myself just guessing what they have, and most of the time I'm wrong.

If anyone has the time, I would really like to see a hand history (preferrably of a SNG) in which you have developed a read on a player(s), with notes on how/why you've made these reads. Perhaps that's a ridiculous request, but it doesn't hurt to ask.

Thanks in advance for the replies. I think this site is an excellent resource, and I appreciate the effort you all have made in educating the students of the game.