Share valuation in case of unlisted public Company

Hi..

Can anyone suggest me  for any guidelines or method to be adopted for valuing shares of  unlisted Public Company...???

Suppose any private Company offers exit offer to the shareholders of Unlisted public Company then at what price the offer could be??? on which criteria the value of shares of Unlisted public Company be determined??

If suppose Unlisted public Company  wants to reduce its share capital by paying off/returning to the shareholders then what could be the price payable??

pls. suggest me..

Thanks & Regards.