I have to disagree with the people who say that if you want to know something about someone, all you have to do is ask. That works only when the truth serves that persons best interest. This might come as a surprise to some, but people lie.
The best way to find out if they're telling you the truth is to ask follow-up questions and get corroborative evidence if possible.
For example if a guy says he's single, ask if he lives alone or with somebody. Watch his eyes when he answers, if they avert yours or he's slow to respond, he's probably hiding something. As the previous post suggested, explain that you like to get to know people before you play and ask if he has a home phone at which you can contact him. If he's serious,
and truly single, he won't mind sharing it. ("corroborative evidence") Tell him you have kids and a sitter at home and see what his response is. If he offers to take you back to his place, he's probably single. If he suggests going to a hotel, he probably isn't.
It's easy to tell "a" lie, but very difficult to tell a series of lies that all support a basic untruth.