If you know that someone is in a relationship, please back off. There is nothing good about making someone else unhappy in order to make yourself happy. Ruining their relationship won't do anything other than hurting the one that you are interested in and you should never want that. If that person truly wanted to be with you, they'd end their current relationship to start a new one with you. Don't try and pressure them.
Nobody likes a homewrecker. Chances are, the one that you want won't even want to think about being with you if you are constantly trying to get them to break up with their significant other. Always remember that there is more than one person in the world. You may think that the person in a relationship is absolutely the one for you, but there are always other people. Wait it out. If it is meant to be, it will happen. Intruding on the relationship will just make the one that you are interested more irritated with you.
It is not cute to be a "side hoe" or "side chick". If the person that you're interested in really wanted to be with you, they'd end their current relationship and start one with you. They'd respect you and their significant other enough to give one of you up instead of trying to have both. Don't make yourself stoop to that level. I know that if I found out that someone was really trying to break my boyfriend and I up to be with him, I'd have a little something to say to the other person.
Encourage love, not hate or disrespect. How would you feel if you were on the other side? Not so good. This is part of bringing back genuine relationships and people like you are the ones who make that hard. You shouldn't ever want a cheater
The relationship is between the two in it. It is not up to you to swoop in and try to make it end. If either of them are unhappy, they will end it themselves. Stay respectful. Always think about how you would feel if someone were to do the same thing to your relationship.
Don't be that person. Would you want to be with someone like that?