Step1
First, determine your spending budget and consider the age and interests of the teen. Does she have a car (for older teens), is into a hobby or has been asking for something lately (within budget, of course). If in doubt, ask her parents for some insight.
Step2
Next, after choosing a category, select an item that you may feel is most relevant to the teen girl. Some great ideas to help when making a gift selection are:
For the fashion conscious teen - Consider giving them a $10 gift card towards the purchase of any item from their favorite clothing store. Many places have sales that are up to 75% off from seasonal returns and clearance items. While a $40 sweater may be a little pricey one month, the same item could be $10 the next.
Beauty - A Bath and Body Works gift card is another great idea. After season sales occur twice a year there and many products are marked down to $1. Allow your recipient to select their own fragrance unless you know for sure they like it, as some scents tend not to agree with people.
Movies - Everyone has a favorite movie that they love, the question is, do you want to present it on DVD or as a movie ticket? If you are unsure, both AMC Theatres and Blockbuster rental store have gift cards available at many merchants.
Museums - For the science lover, be sure to give them a ticket to a local museum or planetarium. Also, there are similar tickets for teens who have an interest in art (gallery tickets), music (symphony tickets) and sports (sporting event).
Lunch on you - A $10 gift card to a favorite restaurant or a hand-written coupon for free lunch at a teen's favorite eatery also makes a great gift, and is one that will definitely be well-used.
For teens with a car - A gas gift card for $10 makes a great present. It is something that can definitely be used; however, it also is an important safety item, as the card can be put away in case of emergency for a fill-up.
Book lovers - Will definitely appreciate a book from their favourite author. Unsure if your recipient already has a book? No problem, all of the major book retailers (Books A Million, Barnes and Noble, Borders, and Amazon.com) all offer either gift cards or e-gift certificates.
Step3
If you really want to personalize the experience though, set aside a spending limit and take the teen girl shopping to a place where your money can really go far like an outlet mall or factory store. Always make sure though, you discuss with her parents allowable clothing styles so there is no confusion about what is appropriate and what is not.