But why? Whats the point?
Well, first off, we need to get to know The Triangle. There's two basic types: what I like to refer to as the equilateral and scalene love triangles. (wow, my geometry teacher was right, I would use triangles in life(even though, somehow, I don't think this is what he was referring to...))
This is what I like to think of as a "true" love triangle. It's one where there's two evenly (or at least very closely) matched guys vying for the MC hearts. These are the kind that create alot of emotional confusion and inner turmoil for the MC; where they have to make an impossible decision between two people they love. This kind also provides an opportunity for the character to grow as they think deep thoughts on what is right for them and find self discovery, etc. Also, another reason we love these so much is because we like to see what she chooses and why she chooses it.
So this is the name I've given to what I think of as "bad" love triangles. This is when one character is obviously the right choice, and the other guys just kinda... there. Now, these kind of triangles can serve a purpose. They could be used as a contrast: to show that Exhibit A is clearly the right man, because he loves the main character for who she is, while Exhibit B just wants her for her body, etc. It can also help the main character to know whats right: Exhibit A loves her, but he does some pretty sketchy things and wants to get her involved, while Exhibit B loves her too, but wants to help her make good decisions. However, when writing these kind of love triangles , never, NEVER, try to make a "bad" triangle look like a "true" love triangle. IT WILL DRIVE YOUR READERS INSANE.
One of the things I hate most is when I read about a girl who has one guy who lusts after her, and another guy who loves her, BUT FOR SOME REASON SHE DOESN"T KNOW WHAT TO DO. It's unrealistic. No one would sit there thinking : " Well, this guy wants me for my body and is trying to get me to do insert-bad-thing-here, but he's kinda hot and I kinda like him. But then there's this guy who loves me and wants whats best for me, and I think I love him too. What should I do?" At these points, I just want to go in and slap the MC.
If you want a love triangle that is confusing and hard for the MC, and requires her to make a tough choice, then make sure you give her reasons to be confused. Make both of the guys people she could be happy with, people she loves. You get a good example of this in Matched, by Allie Condie.
But if your point is to show contrast, to prove that this guy is better for x amount of reasons (great, more geometry...), then don't make your character all confused and wondering what to do.
And honestly, are you just adding in a love triangle because every body else is? Sometimes it seems to me like this is the case. I read a book where you got one guy who the author clearly likes, and wants you to like, and the other guy is just kinda there. Sure, he likes the girl, but she already has her mind made up on the other guy and doesn't really pay attention to him. This just created some pointless complications.
Now, don't get me wrong. I like drama. But give it a reason to be there. If you want to create a complication with two people's relationship by adding in another guy, make sure that the outcome moves them forward.
For example: The MC love this guy, but is too shy to get across her feelings, even though she's pretty sure he loves her back. However, just as things start to move forward, another guy shows up whose all over her and showers her with attention. She doesn't really know how to react, so she lets him do it. The guy she loves sees this, thinks that she no longer needs him and is hurt. This then forces the girl to overcome her shyness and tell the guy she loves that she loves him before she loses him forever.
Get it? If you want drama, give it a reason to be there so that its not always drama drama drama. Because people will get sick of it. We want to see your MC make hard decisions and to grow, and thats one of the reasons why we like love triangles.
Next up : why authors write love triangles. ( don't worry, I promise it will be ALOT shorter)