I don't think there are any rules. As individuals we might set up guidelines that are usually followed but I have done different things and approached my luves very differently each time. Not that it has been a lot! lol
I am attracted to certain traits in people though...humor/wit, intelligence, honesty, kind-hearts, passion, giving and capable of receiving... And there are always exceptions!
I heard, from a movie (go figure) a statement that I find oh so true! "We like people for their good qualities but we love them for their flaws (maybe it was defects)" I think that was the quote, I'm not sure if I have every word correct but you get the picture, right?! I thought this was so accurate, for me anyway.