The most common security concern for your typical Android user is whether the applications they've chosen to install can access the sensitive data stored on their device.
If your app has access to the user's data, then you have a responsibility to make sure that data remains secure. One of the quickest and easiest ways of protecting user data is to take a long hard look at whether your app really needs access to this data at all. If you minimize the data your app has access to in the first place, then you minimize the risk of your app inadvertently exposing personal information. You also reduce the chances of attackers being tempted to try and exploit your application in order to gain access to the sensitive data it's privy to. You should always be on the lookout for ways to create the same effect without your app requiring direct access to sensitive data.
Wherever possible, don't store usernames or passwords on the user's device. Instead, your app should perform initial...