So all Rocky references aside, Tigereye Brew is as close to the most important button for a Windwalker as there could be. How to use it is widely considered a main divider between the good and the great Windwalkers.
What it does
Tigereye Brew is a Windwalker cooldown that increased damage and healing done by 6% per stack. You can use up to 10 stacks at once for a maximum of 60% increased damage and “bank” up to 20 stacks. The buff lasts 15 seconds
How you get it
Stacks are generated for every 4 Chi you consume and by using Chi Brew which automatically generates 2 stacks as well as 2 Chi. Any stacks generated have a chance equal to your Mastery % to generate a second stack. This means that every 4 Chi spent can generate 1 or 2 Chi, and every Chi Brew has the chance to generate 2-4 stacks.
What you do with it
This has been the point of some controversy, but most of that has died down. Basically, the discussion boils down to whether or not you care about the stack count. Some claimed that you should only use it above 10 stacks so you get the maximum buff. Others contended that using it with other damage increases regardless of stacks is the way to go. Finally some argued that it should be somewhat in between.
Regardless of which side you’ve been told, there is only one best way:
Use it for any major damage increase regardless of stacks.
“Major damage increase” is somewhat of an arbitrary term, but most take it as a trinket, legendary ring, or another period of increased damage when a boss is more vulnerable for some reason. Basically any time you’ll be doing more damage anyway, you want to increase that by as much as you can.
Some smaller damage increases like Tiger Strikes or weapon enchant procs are not really sizable enough to merit using TEB on them unless you are close to capping. It should go without saying, but I’ll say it anyway, that you don’t want to waste any stacks that you would generate; so if you get to 17 stacks or so, you’ll want to use up 10 so that you don’t overcap
Here’s where it gets complicated
Serenity and Fists of Fury are also points in time where you are doing increased damage enough to merit using TEB. A buffed FoF will do enough damage to make it worth it regardless of the stacks, as will using Serenity due to the non stop BoK spamming.
In an ideal world you get a trinket or ring proc, FoF is off CD then just as you finish FoF you can Jab and go straight into Serenity. Thats not always how it works, outside of the opener. However, when you see Serenity coming back up, most of your thoughts should turn to finding a way to fit Serenity after FoF and both during the 15s of TEB.
Outside of that perfect scenario you’ll have to practice good judgement in order to get the most out of your Tigereye Brew. If you get a trinket or ring proc or FoF off CD but not the others, you’ll have to decide whether or not to use it and go with lower stacks for the next event. Personally I prioritize FoF over trinkets, and that’s been working for me, but I can’t speak for its mathematical benefit.