If I am interested in you, I will pay hyper-attention to you, especially when I can do so without being seen by you while doing it, in other words, I will study and observe you and speculate who you are, and why you are who you are and why you do/behave in the ways you do, etc.
When I am intrigued, surprised or challenged by you and your existence, unless I am entirely not physically attracted to you, I am "hooked". I love figuring complex people out, and I am attracted to complex people.
If I am interested in pursuing a potential relationship with you, I will make this interest known, by paying you more attention and seeking out your attention. Also, at some point, I will flat out express the interest I have for you to you.
When I feel all

for someone, I am and can be incredibly affectionate!!!
When I like a guy, I like making him feel good, and especially delight in caressing and, or massaging him in such a way so as to make him feel more relaxed, or .....
