I think it's first worth having policies that recognize the modern knowledge worker. Unlimited vacation, hardware budgets, a results-only work environment, optional meetings. No company bullshit. Etc. That way folks won't go "maybe a vacation will help" - because you've already done it.

Of course, that is just removing roadblocks. That's not an active measure. You should be having weekly one on ones with all direct reports (and so on up and down the chain). Rarely when a coworker quits is it completely unexpected. At some point a switch is flipped from "not going to even consider it" to "sure, I'll talk to recruiters." And then the clock starts ticking. In some ways, the organization has already lost if it got to that point.

Raises and titles are not the only thing that drives people; I'd probably argue that's the worst sort of extrinsic motivation. If a bigger title is all that keeps someone working there, you've already failed. As a manager it's your job to know what motivates your people and help get them there accordingly.