I try not to make assumptions about what other people think of me. When I get signals that would be appropriate for a range of possibilities, I try to remember that the whole range is possible and not assume one particular state is true.
Say someone agrees to drive me to the airport -- I don't know whether that means they like me, or they enjoy being helpful and would assist anyone who asked, or whether they happen to be bored and like driving, or what. Or from the other side, if someone doesn't talk to me for months, I don't know whether that means they've decided they dislike me, or they're really busy but would love to hang out if only they had the chance, or etc.
Because I'm keeping all these possibilities open, I tend to interact in a way that would be appropriate for the whole range. And it occurs to me that that may be why my interactions with others tend to get stuck at a particular level of friendly acquaintanceship. If I'm not told that the other person would be interested in more specifically-friend-like (is 'intimate' the right word here?) activities, then I don't know that they are, so I won't suggest them. Things that would be appropriate to the higher end of the range of possible friendlinesses, but not to the lower end, like one-on-one activities or just hanging out without any particular activity in mind, don't happen, because I don't suggest them. Therefore, the relationship doesn't ever move past 'friendly acquaintance' into proper friendship, because the activities that would support a friendship don't happen.
This may also be why I'm uncomfortable with the concept of flirting; the greater the possible range of what the other person is thinking, the harder it is to come up with responses that are appropriate across the whole range. So flirting of an "either I like you romantically or I like you as a friend" sort doesn't bother me much, because those aren't very far apart, but flirting of an "either I like you or I don't" sort gets distressing.
Also, mixed signals (such as someone explicitly saying they think I'm nifty but then never initiating contact) confuse the heck out of me. Generic middlin' multiply-interpretable signals I can deal with, albeit poorly, as outlined above. But apparently-clear yet contradictory signals I really don't know what to do with.
I'm not sure what to do with that, now I've realized it. Staggering up to people and demanding "Do you like me?! How much?" seems both remarkably awkward and highly unlikely to produce accurate responses.