Hi Simita,
To start with, you need to have skill matrix in place. It may be made in excel file wherein you coordinate with respective heads to give you the input on present competence level of employees. Figure out who are experts, intermediate and beginners in that matrix. Certainly experts are critical resources, hence you must retain them. You may plan to move them to higher band, increase their span of work (as explained earlier). Plan training for Intermediate and beginners so that they can move in next competence level.
It is not an easy practice because we have seen that people by virtue of work does not get chance to improve upon their skills and hence they start looking for change. Hence you need to put extra efforts to prepare correct skill matrix and keep updating it.
You may work upon present levels of your employees, put them in categories or bands, finalise the timelines e.g. by what time an employee can move in next category/band. Once decided, plan for training & development requirements and act accordingly. You must have a system to check the training effectiveness e.g. timely performance checks, quiz contests, customer feedback etc..
For your help, I am attaching a ppt on finalising career path across the organisation. You may also share the same during the induction session.
Just think what would you have expected from your management to retain you and in what way. Once you get the answer, you would be able to make any process.
Remember 5W and 1H to make any process. :)
Best of luck.
Anup