To enter the Lockerz Grab Bag Giveaway, you must both have a Lockerz account, be a US resident, and fill out the entry form here.
Once you've entered the contest, all you have to do is create and share your Decalz. Lockerz will be tracking the number of individual Lockerz members who grab every entrant's Decalz. After the contest ends, winners will receive an email from Lockerz announcing the prize tier they are in with a link to select the prize of their choice from their respective tier (note if you are the last person in a tier, you may have only one item to choose from). Prize tiers are set based on retail value of the items in them.