I could never be with someone who wasn't a friend- I've never felt the slightest urge to be with someone who I haven't already hung out with and established a friendship with.
I could never be with someone who wasn't intelligent- not neccessarily academically, but a sharp mind who I can hold an interesting conversation with.
I could never be with someone who let me walk all over them- yes, arguments might ensue, but I'd sure as hell want someone who would stand up to me or tell me I was wrong when neccessary.
I could never be with someone who cheated- how do you come back from that? How do you trust that you won't be cheated on again?
I could never be with someone who has a problem with me being cuddly and friendly with my friends, including those who are of the opposite gender- don't get me wrong, I can see why someone might not like this, and I don't think it makes them a bad person or anything, but I am huggly with my friends, so if someone I was with had a problem with this, then that would just cause anger and awkwardness.
I could never be with someone who doesn't have their own hobbies, or can't spend time apart- I'll be honest, sometimes I'm a bit of a loner, and like to sit by myself, reading, or going on forums, playing videogames, etc. Someone who also has stuff they do on their own, I find good- we don't have to spend all our time together, we still have separate interests.
Luckily, I have an awesome boyfriend who fulfills all these criteria ^^