I don't really have one. 
I look at each job differently.  Depends on what they want.  
I do have enough experience to know if I can achieve the color with MinWax, 
or if I have to make my own with mineral spirits, tint and blo,  
or just go to the SW and have a color match made.
A lot of times I buy the small cans (whatever brands closer to what I'm after) and mix and match to see if I can get it close. Then go buy the big cans and replicate it.
Stain matching can be an art.

PS,  I have thrown a lot of stain ($$) away because of not being right.
Or keep them around for the one job that doesn't really matter,  which almost never comes along.

Figuring out how to do something you have never done is what makes a good challenge.