Should I say:
I believe that {these terms} are the keystones to success . . .
or
I believe that {these terms} are the keystones of success . . .
I’m thinking of
Agree?
Yes, “of” if you want to go with “keystones.” I don’t know your context, but I would probably say “the keys to success.”
The answer, of course, lies in the definition of <i>keystone</i>:
“A central stone at the summit of an arch, locking the whole together.” (Compact Oxford English Dictionary, 2004)
A keystone is a part of a structure, so “keystone of success” would be correct.
“Keystone to success” makes no sense, and is probably confusing <i>keystone</i> with <i>stepping stone</i>, which would lead to a destination.
Bah, previewing’s for cowards anyway! :smack:
You know - I like this better, it is less cumbersome.
I’m using “keys to success” instead - thanks!
I’ll send you my bill in the morning. 
Previewing is the keystone to success in posting.