It doesn't hurt if he is good-looking and charming, in a characterful, from a novel sort of way. But you want him to be able to drive all the way to Mexico. Or Alaska. With you. On the spur of the moment.
I have never done this of course, but I always spend time trying to quell the thought. I tried to explain this to Chris, Chris of the travelling in Turkey and him falling in love with me and him driving me insane (not in a good way), that Chris, because he asked me for a ride on Sunday and so we talked. He said that he had never heard of anyone who wanted to do that every time they found themselves in a bar or pub, and he said that if I ever did end up asking some guy to leave with me that he would think it was all about sex. I told him no, it wasn't about sex, it was about driving far away from the city and anything familiar and probably sleeping awkwardly and chastely in the car. Chris said he didn't get it. He wouldn't, though. He's not the kind who romanticizes and over-thinks things.
There is nothing I want to do more than take the nearest interesting young man by the hand and get in a car and drive far, far away. Leave behind school, work, family, if only for a few weeks. And it's important that the passenger be a stranger because it's only with a stranger that you can imagine the potential character traits and flaws, only a stranger can be placed so insecurely on a pedestal, only with a stranger can the story unfold in a completely novel and unexpected way, a way that I crave. The worst thing that could happen would be if he turned out to be cliche. Or mean. I couldn't deal with mean; I'd kick him out at the nearest truck stop and pick up a hitchhiker instead.