Here are the main traits I look for:
UNSELFISH - why would I want to spend any considerable amount of time with someone who thought only of themself. Sure, we all have to make sure we are happy, but some people go out of their way to make SURE everything they do is all about them. That's bullshit. I do plenty of things to make other people happy that I wouldn't do if I was only taking my own wants and needs in consideration. When in a serious relationship I put my partner's needs on the same level as mine if not above and I'd expect them to do the same.
Intelligent - you don't have to be a genious. But in order to "get" a lot of what I am into, you can't be an idiot. Good conversation is great, we don't have to agree on everything, but at least be able to discuss. I spent 7 years in school, if you don't have at least a 4 year degree you won't be able to relate at all to how I spent the last few years of my life.
Common interests - again, I just ask for a couple things that we can bond on here, not everything.
Basic understanding of fitness - someone who cares about themselves and how they look. You don't have to look like a hardbody, but at least care and goals can help to. Someone who never steps foot into a gym would likely not relate well to me at all.
Honest - it all starts with honesty I suppose.
Other things I like, but are not required:
Good family - this says a lot about a person.
Financially responsible - self explanatory