How can I move and erase the data on my old Android smartphone?

Q I’m about to upgrade to a new Android smartphone and plan to sell my old one, but have two questions. First, how do I preserve all my existing settings and the apps I bought from the Play Store (formerly Android Market)? Second, how can I wipe my old phone so that none of my data is accessible by anyone else?
Simon J

A Android can automatically back up settings, saved data and installed apps to your Google account. On your old smartphone, tap Settings followed by Privacy and, if this feature is available, enable the ‘Back up my data’ and ‘Automatic restore’ options. Your data will then be synchronised to your Google account.

When you first enter your Google account details on the new smartphone, your data will be restored once you’ve logged in with the same account details (but check these same two settings are also enabled).

The option to perform a ‘factory reset’ is also available here. This wipes data from the smartphone’s internal storage and restores it to an as-new state. Before activating this, you should erase the smartphone’s memory card using the Format or Erase option in Storage, under Settings - unless you plan to use it in your new smartphone. This step is important as not all Android smartphones reformat memory cards as part of a factory reset.