Summarize this article in one sentence.
If you don't want to approach the guy directly, talk to other people who know him or the girl he likes. Check to see if they're dating yet, so you can decide if it's a good idea to try to date him yourself. For instance, try asking a mutual friend this question: "Hey, you know Chris? Is he dating Jess?" If you're on speaking terms with the guy, ask him about her. You could poke around to see if he plans on asking her out or if he just thinks she's cute. That way, you can figure out if it's a good idea to start dating him or not.  For example, you could say, "So you think Rachel is cute? Are you thinking about asking her out?" If he's planning on asking her out, you may not want to get involved. He may be too emotionally invested in this other girl to really pay attention to you.  If you don't want to ask him directly, look for clues. If he spends a lot of time with her and talks about her a lot, he may be getting ready to ask her out. Even if the guy likes the other girl and they're dating, that doesn't mean he can't date other people. If both he and the girl agree on it, they may both be seeing other people. You can ask the guy outright or check around to find out more. For instance, you could ask the guy, "Are you two still seeing other people?" You don't want to be the girl who tries to break up a couple so you can date the guy. For one, if you succeed, you may end up in a relationship where the guy doesn't trust you. After all, you did break them up. But, more importantly, it's the right thing to do. Until he breaks up with her or vice versa, consider him off-limits. Even if you think you're meant for each other, keep in mind this person has flaws like anyone else. You may think he's perfect, but that's because you haven't actually been in a relationship with him yet. In other words, you may just be idolizing this person, and the reality might be a letdown.

Summary:
Talk to other people to see if the guy is dating the other girl. Ask the guy about the other girl. Check if the guy and girl are exclusive. Drop the idea of dating if the guy is in an exclusive relationship.