Maintain consistent ongoing feedback on goals, results and documented career path options.  You must balance constructive feedback with opportunity including training programs to help them succeed to the next level they are interested in.  If you keep them balanced on performance today while setting themselves up for success tomorrow, you will put success in their hands and it is a win-win for both of you.

Our website can be a useful tool for you to use with your employees.  You may not have a robust employee training program in your company, but your employees can learn about different jobs, expectations and seminars that could be interesting for them. 

Ultimately you want to inspire them to be better in their jobs; if they start implementing some of the things we recommend in our "things you should do to succeed area", they will feel better about themselves for being proactive, and you will be happy with their performance.

One of the biggest complaints employees have on this issue is when open positions come up they feel they are not considered for them.  Do you best to approach employees before posting jobs, explain what you are looking for.  If someone shows an interest, interview them, talk to them about the training and experience they would need prior to being considered.  If they are not ready this time, work with them to prepare or future opportunities.