1 Answer

From the android forums:

If you've already set up a Google Account on your tablet:

1. Try entering unlock patterns several times right in a row. It *should* ask you to enter your Google Account info as an alternative way of letting you in, after which you can turn off pattern locking or set a new pattern.

2. If you set up a Google Account and the tablet isn't asking you for that info you can try to unlock it from this page:
https://www.google.com/accounts/DisplayUnlockCaptcha (this might only work on hardware authorized by Google, I'm not sure)

3. BUTTONS! There is usually some combination of button presses on boot that can get you into a "reset" or "safe mode" where you can reset it. It varies from tablet to tablet, however. For example, on my Haipad M701-R when I flip the on/off switch off and then on, short press the "end/sleep/power" button and immediately press and hold the "Menu" button through the boot process I go into "Safe Mode."

Also, some APAD tablets have a small, unmarked hole on the side of them that you can stick a paper clip into and press a soft-reset button. No idea if that clears an unlock pattern though.

4. If those options don't work, or if you have not set up a Google Account (either because you bypassed it or you have a tablet without official Google apps on it) another option is to use ADB (Android Debug Bridge) to unlock it. Go to Google and download the Android SDK (if you haven't already) and install it. If you're on Windows you'll also need the USB drivers.

1. Plug the tablet into the computer via USB and turn it on/boot it up.
2. Open a Terminal/Console and change directories to your Android SDK /tools/ folder.
3. Enter ADB commands. On Windows these will be "adb.exe" and on Mac/Linux "./adb" - I'll just use "adb" below for simplicity: 

information source: http://www.androidtablets.net/forum/android-tablet-usage-tips-tricks/6280-forgot-your-unlock-pattern.html