(FORTUNE Magazine) – Now that the executive job market is finally showing signs of life, smart companies are once again starting to worry about how to keep their stars. What makes a highly valued executive decide to quit and take a better offer elsewhere? Conversely, what induces him or her to stay put? Headhunters, on the front lines of trying to pry very accomplished people out of organizations, clearly have a vested interest in figuring that out, so executive recruiters Morgan Howard Worldwide (www.morganhoward.com) decided to do an informal study of the question.

Hoping to entice people to stay just by offering them more money? Good luck. "It's not so much the amount of money as the sophistication of the pay structure that matters," says Marc Lewis, Morgan Howard's president for North America. What people really want, it seems, is a clear upward career path and the autonomy to develop their own ideas without plowing through a pile of red tape. It also helps to have a CEO with a vision (yes, the V-word) that is grand yet realistic and that he is willing and able to explain to everybody else.

If you can't quite swing all four of those, even one or two might do. Lewis calls Dell a "great example of creative equity compensation, a bit ahead of its time." For years now the company has offered its senior managers a combination of various wealth-building goodies, not just stock options, to ensure that their portfolios weather the stock market's ups and downs: "It's hard to get people to walk away from that," says Lewis. For well-defined career paths and the autonomy to innovate, General Electric takes top marks. "Jeff Immelt is continuing Jack Welch's legacy. He's fanatical about investing in talent," Lewis notes, adding that Intel runs a close second. When it comes to what Bush the Elder used to call the "vision thing," Cisco Systems chief John Chambers, who is "charismatic and close to his executive team," inspires intense loyalty.

Lewis is the first to admit that a company that's hard to recruit from today may not be so tomorrow. IBM, for instance, used to be a tough nut to crack, but under new CEO Sam Palmisano, people at the vice president level and above have gotten a bit more willing to take headhunters' calls. "It's not so much a vote of no-confidence in Palmisano," Lewis says. "It's just that, with any big change in direction at the top, there will be managers who no longer see themselves fitting in."

Meanwhile, some companies have cultural quirks that make them easy pickings for headhunters. Citigroup, for instance, has reorganized itself several times in recent years. "Every time you upset the apple cart, managers get more practice in the art of selling themselves," says Lewis. "People at Citigroup have been trained to be terrific job hunters, so they're open to outside offers too."

Predicting what will motivate any one stellar performer to stay is, to put it mildly, an inexact science. The surest way to find out what would keep your stars from heading for the exits? Ask them.