In the realm of YA writing in particular, slang of any kind is tricky, tricky business.
Slang and common expressions can make a teen voice feel more authentic. As someone who spends every workday listening to teenagers talk, I guarantee they're not pulling exclusively from an official dictionary.
Then again, slang is—by its nature—fleeting. A few bits and pieces work their way into the long-term vernacular, but most are solidly dated. Just think about "groovy," "bodacious," and "fresh." You just had certain decades flash through your mind, right? Maybe that's a good thing. Maybe that instant association is what you need.
More often, I'm thinking that's not a good thing.
Let's go back to my students for a minute. There are some who spout a near-constant stream of "totes obvi" and "YOLO." (The one who says YOLO the most keeps doing it out of context. I'm not sure he really gets it. Or he likes to be annoying.) And here's the thing about super of-the-moment phrases. It only takes about two minutes for the kids to sound like they're trying too hard.
And it's even easier for an author to sound the same way.
So how do you deal with it? Stick to the more long-standing forms of teen-talk? Use a strict rule like one super-trendy term per fifty pages? Only let a side character use them, make it their "thing"?
Honestly, I don't know. I'm curious what you've found works, either from a writing or reading perspective.
I tend to work around it by writing science fiction and making up my own slang. Mindy McGinnis thinks I'm good at it. Hopefully others will agree.