Summarize this article:

" Before getting rid of your phone, remove sensitive personal information like phone numbers, addresses, account numbers, passwords, voicemails, and text messages. Most phones let you clear this information using a "factory rest" or "hard reset." These options are typically located under your phone's "Settings" menu under the "Backup and Reset" section. Check your phone's owner's manual or device manufacturer website if you're having trouble finding the reset options—devices vary in their methods. The second method of information storage for phones is through SIM cards and external SD cards. If you're maintaining the same phone number, you can remove these cards and transfer them to your new phone (if the new device fits with your specific card specifications). If you're changing numbers, destroy them or erase their information via the "Settings" menu.  SIM cards and SD cards can hold information like phone numbers, photos, and other sensitive data. If you're selling your phone to someone with the cards intact, be sure to wipe them. SIM cards are located underneath the battery and slide out of a small compartment. SD cards are thicker and are usually found on top of the SIM card pocket, or inserted into the side or top of your phone. After deleting your personal information, do one last check to make sure everything is clear. Look in the following areas:  Phone book Voicemail Emails and text messages (sent and received) Folders (downloads, pictures, music) Search history Call or visit your provider to purchase a new phone. Once you have new phone, you will insert either a new or old SIM card connected to your account and effectively remove service from your old phone. Always get your new phone up and running before selling your old phone. If you have an online account, you can likely make arrangements to have a new phone (and a new SIM card if you're getting rid of your old one) shipped to you via your cellular provider's website.

Summary:
Wipe your personal information through a "factory reset. Remove SD and SIM cards. Check your phone one last time prior to selling or recycling. Call or visit your cellular provider to arrange for new phone service.