In real estate, they’re “location, location, location.” And in becoming a musician, they’re “practice, practice, practice.”
What are they in some area of interest to you? For instance:
The three most important things in a healthy garden are compost, compost, compost.
In posting an inane item in a forum: blah, blah, blah. 
I suppose for an editor (like me) it could be “details, details, details.” 
In photocopying: collation, collation, collation.
On this board?
Citre, cite, cite
3 most important things on your way out the door:[ul]
[li]Keys[/li][li]Money[/li][li]Identity[/li][/ul]
[ul]
[li]Prime[/li][li]Paint[/li][li]Repaint[/li][/ul]
It’s much more than that, but that’s the very basics.
In poly relationships, it’s “honesty, honesty, honesty.” Can’t think of another hobby I have that can be quite that simply distilled.
In my job, it’s: leave your name, leave your number, and don’t call back until you get a return phone call.
At home, after a rough day, all I want is: peace, quiet, and to be left alone.
In the field of EMS, it’s document, document, document.
Anything horse related…1) Check your tack 2) Check your horse 3) Check your insurance policy!
According to my business professor, the three “C’s” of credit markets are “character, character, character.”
In working with toddlers and their parents: understanding, understanding, understanding.
For me, historical research is checking, rechecking, and checking again. “Patience, patience, patience” come a close second.
I’ve contemplated this on the Tree of Woe.
My job too. Many’s the time I’ve saved my butt by pulling out a piece of paper and saying, “See? I did what they told me to.”
And many’s the time I’ve pulled out a piece of paper and said, “Whoops. That was my bust.”
For Quality systems, it very similar:
documentation, documentation, documentation.