I like to think I'm pretty good at reading people. I find that I can usually figure out what someone is thinking pretty quickly, and before long I understand their thought process. I use that to deal with them when I need to. The negative view is that I use that skill to manipulate people, and while I can't deny that there may be some truth to that, I like to think that I use it more to find outcomes that satisfy everyone. It can be an extremely useful skill in advancing at work, in particular.
I do this mostly by paying attention. I'm nearly always paying attention. I listen to everything people say, and I store it away. Later, I use that information to build a holistic profile of people. Nobody says or does anything in a vacuum, you always have to put it into the broader context. I take all the context I have on that person specifically and fill in the gaps with what I know about their personality types, people like them, or myself. After some time, I can usually pull together a pretty good picture, and I use that to frame my interactions with them.
That's a very sterile and scientific way to describe a very organic process. It's not like I'm keeping notes on people on purpose, I did this for years and years before I even realized what I was doing. I still do it without thinking about it. It's just a part of who I am, and how I deal with people. It also sounds way more creepy when I write it out like that.
While this is a very useful skill to have, the biggest problem is that I find it is most effective by far as a reflective process. That is, I interact with someone and gather a lot of information, then I (usually subconsciously) analyze it later, and next time I interact with that person I am far better prepared. That's great, except you don't always get a second chance to interact with someone.
What I am really, truly atrociously bad at is reading someone in the moment. Picking up hints and figuring out someone's intentions in real time just doesn't come naturally for me. Mix in a not-so-healthy dose of social anxiety, and I'll often struggle with maintaining "small-talk" type conversations too. As you might imagine, this makes things particularly difficult for me with women. I just don't pick up on the signals that they're interested in me, and I'm usually so preoccupied with not killing a conversation, that I don't have enough mindshare to watch for them.
Of course, hours later (right around the time that I'm figuring out all the perfect things I should have said earlier), I'll clue in. By that point, it's usually too late. It's incredibly frustrating, and I have no idea how to fix it, other than practice.
The worst, however, is realizing weeks or months later that I missed something. That happened to me recently, and it really, really sucks. I had an opportunity for something, and I missed all the signs. Worse still, it happened over the course of several weeks. I had the chance to take in everything I needed, process it, and still had an opportunity to act on it. This is supposed to be what I'm really good at! Unfortunately, other things in my life at the time had me completely preoccupied, and I missed it all. I only just clued in, and short of not at all subtly manufacturing another opportunity (and I really can't think of a way that doesn't come off as borderline creepy at best), the chance is probably gone. At least gone for now.
Missed opportunities suck.