What are some content hacks to get more engagement?

I recently found out a great e-commerce hack to increase sales: make your product have free shipping. Just increase your prices to include the cost of shipping. I got way more sales on eBay just by having free priority shipping.

It got me wondering: does anyone have any good content hacks that get more engagement/clicks/likes/comments/upvotes/etc.?

One thing that has worked for me in the past is to make my titles a bit vague. For example I made a video about the explosive growth of the coffee shop industry and titled the video "The Coffee Shop Explosion" which, yes, is clickbait, but the video got way more views with that title than with something more descriptive.

I'd love to hear your content hacks!