Android Pattern Lock Factory Reset
If you have set a lock screen pattern, it can be recovered using the default Google account. After entering the pattern incorrectly 5 times, tap Forget password at the bottom of the screen. Enter the Google Account username and password associated with the device to unlock it.
Make sure either your data connection, or wifi connection are turned on to ensure that this works !!
If you don't remember the Google Account information or are using a different screen lock type, the device will need to be factory data reset. You can find factory reset instructions for most android devices in the Phones section.