Here are some ways that I can tell what my opponent is trying to do and what they MIGHT be thinking about.
1. The first way is when it is there turn quickly glance at their eyes and the look at where on the board they are looking at. If you know where on the board they are looking at, then you might be able to figure out there plan more easily than if you we're focusing on a place where they are not thinking about.
2. The second way is also by looking at them also. Look at there facial expressions. DO NOT stare at them for more than 4 or more seconds. You will look like a creep just staring at them. But if they look worried you can tell that you have a good move on the way. If they look excited then they have a plan they are about to execute. Though they might be bluffs, they are usually not 60% of the time. You want to check to see if there bluffing by simply looking at the board and see if they have anything they can do up there sleeve.
3. Once again you are looking at them but not at there face. This is a god way because you can look at them for a slightly longer time. You want to look out for there body language. For example, if they are stretching, sitting back, or paying more attention to other people's games more than their own, then that might show that they feel that they are in a good position or feels good about anything that is going on In the game. Another sign is that if they are contracting really hard and that they are at the edge of the chair and focused about the game. That shows that might show that they are think really hard or that you made a very good move and they need to find a way to counter it.
4. This one is pretty obvious but for the people that don't know. If your opponent offers a draw, that usually raises the flag that they feel they will loose or don't feel confident about the position. Usually you would decline but they might have a point. The position may be drawn and you just don't know it. But you can always accept it if you want to after thinking it over for a while and feel that he can come back and leave you in the dust with a bad position.
Well that's all I can think of now, once I find more ways I will share it with you. But if tHere are ways that you use, please share it with the chess.com community. I would like to know how you might figure out what they might be doing. That's all for now and I hope you enjoyed.