Your first step is to decide whether you want to get top dollar for your smartphone or if you just want someone else to deal with the hassle for you.
I’ll Sell My Cell Myself
First up, this is a good time to mention our friends over at Glyde. Their service is probably one of the easiest ways to sell your device while still maintaining some control over the price. A lot of the precautions that you have to think about with other avenues for selling just aren't an issue when you sell through Glyde. For more information on the ins and outs of the process, click here.
Another great site that has built in easy-to-use buying and selling infrastructure is Swappa.
If you want to a wider landscape upon which to sell your device, or if your device isn't one that can be sold through a marketplace like Glyde or Swappa, take to eBay, eBay Classifieds, Craigslist or similar.
Figure out what’s a fair price to ask. Depending on the condition, currency and desirability of your phone, you can hope to get anywhere between about 30% and 70% of the original ticket price. Check other sale listings to gauge how much you should ask for.
Create an ad with as many pictures of your phone as you can offer. Clearly outline the condition of the device you’re selling and how much it'll take for you to part with it. Search for your phone on GSMArena to get detailed specs to go along with your listing.
Be prepared to haggle when interested parties start emailing.
Don’t accept fake cashier’s checks or wooden nickels, don’t deal with escrow services or other likely scams. Basically, if the person who’s offering to buy your phone can’t or won’t stump up the legal tender to do so, move on to another potential buyer. Read Craigslist’s scams section for common scams.
The site ecommerce-guide.com has a useful article on classified selling. While the tips are specific to Kijiji (since re-badged eBay Classifieds), the information holds for all classified selling.
Someone Else Sell My Cell
If you’d rather not deal with the hassle of selling your device on your own at all, there are sites that will buy it from you (making it super easy to cash in) but will offer you less than you’d get if you did the work yourself.
Gazelle.com is a great service that takes all the work out of offloading your erstwhile mobile. All you have to do is tell them what kind of phone you have and what condition it’s in, including what accessories (like the all-important charger) you have. All of these variables are factored in and Gazelle will offer you a price based on your answers to their quick questionnaire.
They’ll then send you a pre-paid shipping box which you'll use to send your phone to them. A couple days after receipt, you’ll get your money.
I Don’t Want to Sell My Cell
Lifehacker has several interesting ideas for things you can do with a smartphone that’s reached the end of its usefulness to you but that you’re not quite ready to part with yet.