How to know the Market value of a company?

This is not an easy one as all fund managers on earth are looking for the answer and very few get it right all the time. Just look at the performances of all Vinacapital, Mekong Capital, Dragon in the past 3-years lost money... they did not get the right market value.

There are 3 main reasons for that (and for why it is the most difficult in business is to become a skilled investor):
#1 Market value and Intrinsic value. You can evaluate -almost calculate and intrinsic value of a company- based on what it really can return to your 100$ investment. But when the little investor jump in the stock market with a "crazy fever to buy", the Market price jump for no reason with no logical reason. This is called a bubble when the Market price goes much, much higher than the intrinsic value -read Warren Buffett letters about this).

#2 technically there are 4 ways to calculate the Intrinsic value:
1) Economic profit approaches (Residual Income, EVA)
2) Discount models (DCF)
3) Multiple-based models (EV/sales, EV/EBIT, EV/EBITA, EV/EBITDA)
4) Peer-group comparisons
you can read any book to get this right but you also need to consider some economic data and make optimistic/pessimistic assumptions to get and idea (then come the crazy buyers or sellers who create the Market value)

#3 Leadership & Management, is the most difficult that fund managers miss out most of the time because it is human being making decisions on the future that they don't know (leaders are not "thay boi"). Leaders sometimes make wrong choices -myspace Vs facebook, Nokia Vs Iphone, Bac Tuyet Vs Phong Phu textile? Sometimes they mis-manage REE invested their cash in the stock market and lost millions, Vinashin started many companies and lost it all...