It's a crapshoot.
Obviously, there are ways to maximise your chances of your hire working out, i.e. vetting, fit, desire, reputation, etc.
However, even the "best" hires on paper often don't work out.
Therefore, while putting your best effort into making a good hire is important, no less important is also keeping flexibility. That means:
1) Not getting married to any single coach and being ready to cut ties *the minute* it's clear it's not working. UCLA AD's in the past have loved to drag these things out and it's always a failure.
2) Related to #1, don't put yourself in a bind by overpaying. You're better off taking a chance on a cheaper up-and-comer, who is also hungry, energetic and maybe has new ideas, than a big, established name, who also is no guarantee and happens to come with a $50M buyout.
My 2 cents