For me it's more about personality than looks. I can meet a guy who is really good-looking but be turned off within minutes by his attitude/arrogance/whatever. Conversely, I can meet a guy and be impressed with his personality and only then suddenly realize just how good-looking he is (don't ask me how that works, lol).
That said, I don't assume that good-looking guys are going to be arrogant or whatever else. I also don't assume that they will find me particularly attractive or unattractive - when I was younger I was intimidated by them and assumed that I wasn't their "type" or pretty/hot enough or whatever, but now I just think of them like anyone else and assume that they will react accordingly. (Sometimes they don't seem to know how attractive they are - it's almost funny to watch.)