How do you act towards someone you are interested in romantically / crush on?

It took me a stupidly long time to realize people react differently. Duh, obvious right? Still it didn't hit me until much later on. I'm now curious how others act.

I unfortunately give too much of my time and energy to that person and get sad when they don't reciprocate the same way. I'm working on this tho, and I don't blame them in any way. But yeah, in therapy it made me realize that even IF the other person were interested me in back, they might not do the same thing I do because we are just different people.

So how do you act? I'm asking, just for fun!