What are the components of a good April Fools joke?

Okay, so we all know that some people feel that telling you any random statement, and you in turn believing it constitutes an April Fools prank. But we know better than that. Just by telling someone that you aren’t feeling so well today and them giving you the appropriate “Oh that sucks” response doesn’t mean that you fooled them. That’s ridiculous!

So will you help me make up the “rules”, if you will, for a legit April Fool joke?

Feel free to use this thread to reveal some of your past pranks but please do try to answer the title Q too!

Happy April Fools :)