Some of you may have already seen download links locked for users, forcing them to reply or thank the post to get the hidden content displayed.
Here's a quick tutorial showing you how to hide something in your post until the user does what you want to get it.
When creating a post or a thread, you have a text toolbar with different options, here are the ones to use to hide pictures, download links, methods etc.. :
Just click on the button you want and it will add automatically the Hide tags, then write/copy your content into these tags before posting the thread.
You can ask a user to thank you (by clicking on the "Thanks Button) to get REP
, to reply to the thread so that it keeps itself at the top of the forum, and finally if you consider the user needs minium posts, you can mention the number of posts when clicking on the right button.
If any questions don't hesitate to ask here