Don't accept personal checks: A less-than-honest buyer could easily write a bad check, leaving you in the lurch should it bounce. Instead, either use a service like PayPal or request a cashier's check or money order. This way, you can guarantee that you'll get paid.
Don't make your buyer wait: Ship your phone as soon as you can after you receive payment, and provide your buyer with a tracking number if possible so that they can get a better idea of when to expect it.
Be honest: Disclose any damage to the phone, and mention if anything is missing. Being up-front now will prevent hassles later.
Take lots of good photos: You'll want to provide plenty of photos that show the condition of the phone. Make sure you have good lighting, and try to take the photos on a clean, uncluttered desktop.
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