Hi Kishoryy,
I am also working in a manufacturing company. In our company, I have worked on manpower planning. The steps/process are as follows:
1) Collect the data from every location (only those locations where your company's other plants are located).
2) Then try to compile it department wise and also plant wise.
3) Then try to extract the age and number of years of experience that a particular employee (management staff & operators) in your company has.
4) Then identify which employees (including both categories) are retiring by the end of 2008-2009.
5) Then assess if you need more people or if you can transfer them from one department to another, or if you can outsource the job (operators level) in case you want to reduce the manpower in your shop floor.
This is the approach we have taken in our company.
Regards,
Ankit