Require entrants to submit a secret code that you can share via social media, put on your website or hide in a number of other places.
Secret Code Actions are a fun way to engage with users and gives them incentive to pay more attention to your brand. No matter how you distribute a secret code, entrants can use that code to claim entries for your giveaway campaign.
There are so many creative ways to distribute secret code(s):
Release Secret Codes on social media intermittently while your campaign is running. That way for the duration of your campaign, your followers will be checking your accounts closely for the secret code drop.