While working as a spa coordinator at a luxuryresort in Stowe, Vt., Laura Crandall got a sense that her boss was unhappy and thinking of moving on. So Ms. Crandall trained for her boss's job by volunteering for more work, pursuing mentorships and attending management seminars.

The effort paid off. Her boss resigned a year later, and Ms. Crandall was promoted to director. 'You have to show up and deliver,' says Ms. Crandall, who is now a workplace communication consultant. 'You can't just talk about what you want and expect to get it.'

Being the next in line doesn't guarantee that you'll be promoted, but there are a few things you can do to improve your chances, such as bolstering your qualifications.

Many would-be successors are actually underqualified, says Paul Glen, a management consultant in Los Angeles. 'They just don't realize it because executives tend to have a narrow, circumscribed view of their boss's job.' Also, many No. 2s are hired to serve in specialized roles that don't necessarily require leadership skills. That's why it's important to develop the hard skills early so you can prepare for when your boss does leave.

A recommendation from your boss is the best way to land a promotion, so start earning that support by letting him or her know that you are interested in advancing -- just don't sound like you're planning a coup.

Inquire about your strengths and weaknesses so you can fill knowledge gaps with some professional development. Also request additional work that helps you build experience and allows you to manage projects from beginning to end.

Learn what your boss does by following his or her daily routine. Observe the interactions between your boss and other employees and ask to collaborate on tasks so you can gain an inside view of the job.

Go outside of your work group and talk to peers of your boss, who can offer you a companywide perspective on the management chain. Seek cooperative managers who would be willing to mentor you or at least offer advice. This can include talking to your boss's boss. Immerse yourself in industry trends so you can casually converse fluently about company issues and make thoughtful contributions during meetings.

Over all, pursue activities that increase your visibility within the company, such as volunteering for a charity the company supports. You may get noticed by board members or at least remembered by senior managers who may be tapped to make employmentrecommendations.

'Don't try to compete with your boss or show him or her up. You don't want to appear ruthlessly single-minded,' says Gaby Cor[aacute], a Miami executive coach.

Distinguish yourself by doing your job well and being supportive of your boss, even if you don't agree with his or her processes. Being able to toe the line can also be a valued trait.