Your key block, on one sheet
The same task on the same key, on every character: 1 is always your main button, E your interrupt, Z your small defensive. Print it, or keep it on your phone or a second screen while your fingers learn it.
Your own block, from the game
In the game, type /mh block and press Cheat sheet. Copy the code and paste it here.
The code stays in your browser. This device remembers it, so the page opens on your block next time.
No addon yet? Pick a spec
How the block usually looks for that spec, as if you knew every spell of it. The code from the game shows your own talents.
Block D holds your own things on the Alt keys: Midnight Helper leaves it for you. The places with a potion, a Healthstone or a trinket are items: you put those on the key yourself.