Companies that are winning—even really big, old ones—never have a retention problem. Everyone wants to stay, and when someone does leave, it's really easy to get someone great to take her place. Companies that have a retention problem usually have a winning problem.

Focus on retaining the magnets—the great architects and managers (or their equivalents) who attract and hire other great people. If you keep a critical mass of them, retaining everyone else becomes much easier. Lose them and you lose everyone.

Clean house simultaneously: fire the VIPs ('vesting in peace'), the 'summertime soldiers' who only joined after you were already successful, and the mediocre performers. This immediately lifts the morale of your remaining stars and frees up comp budget to reallocate to them.

Nuke all matrices, dual reporting structures, and shared services. Push QA, docs, build, etc. into the product divisions and tolerate the overlap—your best people will move so much faster that it's worth the duplicated headcount.

Re-recruit the best people who already left. Many have discovered the grass wasn't greener at the mediocre startup or other big company they jumped to. Give them fat packages tied to the new mission and bring them back.

When someone wants to leave for a startup to 'build something,' make them a deal: stay two more years, take a bigger job with real responsibility, and you'll personally introduce them to the right startup or VC when they're ready. Most big-company people are bad at picking startups anyway, and they'll be far more valuable in two years.

Don't create an 'innovation group.' It tells the rest of the organization both that they're not supposed to innovate and that they're the B team—a one-two punch that wrecks the culture. Same logic kills programs like Google's Founders' Awards: big spot bonuses to a few create backlash from everyone who didn't get one.

A company in crisis often has a severe narrative problem alongside its business problems. Stories don't change by themselves—change the story. When all else fails, do a 'shake and bake': a big transformative deal that at minimum reinjects energy, though you can easily destroy the company doing it.