Why don't we have Life Hack thread like we do have Media Threads and Rationality Quote Threads?

Well, now we do.

I'm copying in the comments some hacks previously written about by others for your convenience, also check out the Munchkin post if you haven't, there are many interesting hacks there. Timewise, I've made it quarterly because it is harder to face a life hack than it is to face o quote, so less frequency may improve average quality. Below is a suggested description for them with structure taken from media threads. Any further ideas on how to improve the thread are welcome and should be made at the Metathread tree.

This is the quarterly thread for posting Life Hacks of various types that you've found that you enjoy. Four main thread-trees will be in the comment section.  

1) There is substantial evidence for it  (please post pointers to it)

2) I tried/ Friends tried/ There is some small evidence for it

3) Seems like a cool idea

4) Metathread

Rules:

• Please avoid downvoting recommendations just because you don't personally like the recommended material; remember that liking is a two-place word. If you can point out a specific flaw in a person's recommendation, consider posting a comment to that effect.
• If you want to post something that (you know) has been recommended before, but have another recommendation to add, please link to the original, so that the reader has both recommendations.
• Please use the comment trees for level of certainty regarding effectiveness.  There is a Metathread for comments about future threads.
• Please post all Hacks separately, so that they can be voted up/down separately.  (If they are strongly related, reply to your own comments.  If strongly ordered, then go ahead and post them together.)