Kowsar Hossain

If you want to make coupon code as a required field, this plugin will help.
During checkout when a customer will try to place an order without entering any coupon code, checkout process will be interrupted and customer will see an error notice.
You can configure the error notice text from “WooCommerce>Force Coupon” menu from admin panel.

Force Coupon for WooCommerce

A lightweight WooCommerce based plugin to force the customer to enter a coupon code during checkout

Soflyy

<h4>Market your content virally on social networks by forcing users to perform a social action before accessing your protected content.</h4>
Check out the 2 minute demo video on YouTube: http://www.youtube.com/watch?v=aheR3_ROt94
Like To Keep Reading is a WordPress plugin that forces visitors to Like you on Facebook to access content on your website.
You can protect entire pages or posts, or just sections of pages or posts (our favorite) – i.e. your visitors can read the first two paragraphs and then must click the Like button to keep reading.
You can force visitors to Like your website homepage, any sub-page/URL on your website, or your Facebook page.
Like To Keep Reading also has optional Google+ and Twitter integration – so instead of Facebook Likes you can get Google +1s and Tweets from your visitors in exchange for access to your content.

Like To Keep Reading

Get more Facebook Likes, Google +1s, and Tweets by forcing users to perform a social action before accessing the rest of your content.

Force Coupon for WooCommerce vs Like To Keep Reading