First, you must realize teens are ruled by peer pressure! This means that no matter what they get, all they want is the latest fad! Teens have their own culture and it's hard for us outsiders to keep up with it! Usually the best we can do is narrow it down as much as possible.
There are some general gift categories that can be safely applied to teenagers. Music is a good one. Clothes, and electronics are great areas to search. And, of course you can never go wrong with Bling! Gold and silver seem to be the current preferred jewelry. Another good area to explore is Grooming. Teen are very conscious of their appearance and are always trying to look good!
Modern teens thrive on socializing and live on their cell phones and tablets.These are generally updated every 3 to 4 months, so a new one is almost always welcome! Just be sure it's an up-to-date model and not one that's about to be replaced (teens like new).
When it comes to clothes, your teenager is probably going to have a much different idea of fashion than you. They may or may not want that sweater, and those shoes are probably out of style. Your best bet is to stick with something simple and reliable like Levi jeans (always in style).
As always, teens like interactive video games! The Xbox one console has just been released, but be sure they aren't a Play station 4 fan or something else. There are many popular games available and you should be prepared for an overdose of violence when searching. Grand Theft Auto and Assassins Creed are popular.
Jewelry is a great idea for a Christmas gifts! At this age both girls and the boys like lots of Bling. And nice jewelry and accessories are not nearly as expensive as you'd think! Jewelry has more flexibility in style and fit.
As a "word of caution" be careful asking their friends what your teen wants. They don't keep secretes well at all. Seem no matter what you get, they'll probably give you a nice, polite thank you, and never use it! Ah well, unless you're grandma with this years check, I suppose that's to be expected. Hmm, wonder about gift cards this year.