You may find it helpful or interesting to read a collection of interviews
I did with a few people about how they figured out their sexual orientation after a period of questioning or confusion. I don't think there's any one way to find out; some people have a bit of a lightbulb-turning-on moment and for others it's more of a gradual understanding, but I found that hearing other people's experiences was really helpful for me in my own process of figuring things out.
Like Jacob, I get crushes pretty easily and I'm very aware of it, so for me it's easy to tell, but something I've learned is that a "crush" is one word to describe a pretty wide range of feelings, and different people can experience them pretty differently. In general, I don't tend to have "celebrity crushes," only crushes on people I know personally to some extent, and for me the big tip-off that I'm feeling a crush is a strong desire to get closer to them, to know them better, or for them
to want to get close to me