Activation Lock

Usually there is nothing you can do, you can't go past the Activation Lock without knowing the Apple ID and password. But since the iPad was previously linked to your Apple ID, you may be able to reset your Apple ID's password using:

http://iforgot.apple.com

On the activation lock page is a major hint as to what you used. It should look something like: o*****@hotmail.com (or some variation of that). That is the email address you used to set up the iPad.

Use this link to help you find it: If you forgot your Apple ID - Apple Support

If you are unable to recover the ID, the only other option available to you would be to find the original purchase receipt, the one with the iPad serial number on it and take that with you to the Apple Store Genius Bar for assistance. Apple won't help you without valid proof of original ownership.