Before you sell any phone, you want to make sure that you erase all of your data on it. Most phones nowadays are pretty good at allowing users to manage the data they put onto the device, including erasing all of it. You may want to remove your SIM card. SIM cards normally hold all your contacts and call logs, and the next user will have no need for your SIM card, so make sure you take that out.
Like @RaNar mentioned, you want to remove your micro SD card prior to selling it. I haven't heard of a phone that came issued with a micro SD card. However, if you must sell the micro SD card with your phone, make sure that you erase all the content on it, and format it with the correct file system. You can read up more on how to do that online.
I hope this helps