I understand having no intuition to go by when you first encounter the term, but it's not anything hard to remember, and it really does follow logical English rules once you know it. A trans woman is a woman. A trans man is a man. Just ignore the "trans" part and go with the other word, like you would if it was any other adjective like "gay" or "tall". If you're confused by whether this refers to their past or present state, remember that we tend to describe people how they are currently.
Part of the point I wanted to bring up is that there is no way of knowing in which way it is describing them as they currently are from the word alone, though. Unless you already know how it is used.
I'm approaching this from an entirely internet based context, by the way, as 100% of the times I've seen this asked has been when unclarity has arisen on the web because text articles or posts give little personal context.
I don't get uncertain about what's being referred to myself any more, because now I know (and knowing is half the battle). I just wanted to respond Descan's post and say that no, I don't think isn't particularly self-explanatory to the uninitiated, so it shouldn't be a surprise that people ask about it (particularly people who care about not mistakedly referring to others in an incorrect way).
Why is this discussion still ongoing? It was supposed to stop long ago.
It's not the sane discussion any more.