Really depends on the teen and some input from parents if you are not as "in the know" as they are. I have a 16 yr old daughter..and magazines are a great idea! For girls..as far as what mine likes.....silly slippers and pj pants..the sillier colors the better for her! Last year, just to have a few more "for fun" things for her to open (as we got her one BIG spendy thing and wanted more opeing time)...I got her some cheap, on clearance boot type slippers at old navy..funky colors and stripes...and she loved them and still wears them all the time!
Ear buds for MP3 players are about $20...crazy colors and "fun factor" and who doesn't need a new pair. I love the Skull Candy brand..definately good quality (and this is from an adult who can buy whatever brand she wants, not necessarily budget ones)..they have great sound, fit comfortable and as I said..fun colors....
My daughter loves owls..anything with cute owls on them...do any of these girls have a specific "like" in this way? (we do cooking aprons and pot holders as she bakes alot....jewelry/keychains, socks/slippers, shirts, pj's, etc...notebooks, journals...all of it!) Any tshirt, inexpensive necklace off ETSY.com (they have these sellers who do scrabble tiles with things on them..add a cheap chain and shipping and they are fun)...keychains if the 16 yr old drives or if they are all home alone after school and have keys of their own?
For a boy...no clue! I have a brother in law with 4 boys and another with 1..and I am clueless!!!!