I must be the first kind, because I've never noticed a girl being interested in me.
But now I'm wondering how many times I've missed the clues.
In my experience the clues are usually subtle, where they become more self-conscious about looking pretty and being proper whereas in front of people they don’t have a crush on they may give no effort.
Also, from a man’s perspective, the effort women give is also usually quite subtle. Western women will rarely just come out and say “I have a crush on you, will you be my boyfriend?” Instead they’ll do things like get their nails done, dress better, and do their hair. The thing is that most men really don’t seem care about that stuff so it isn’t always obvious that they’re attempting to be more attractive to get our attention.
There’s actually a huge gap in what men and women think each other want most of the time. Just my experience, but it’s good to be aware of. It could really help I think.