As I know blue chip is good stock but how to determine a stock as a blue chip?

A blue chip stock is the stock of a well-established company having stable earnings and no extensive liabilities. The term derives from casinos, where blue chips stand for counters of the highest value.[1] Most blue chip stocks pay regular dividends, even when business is faring worse than usual.

Source: http://en.wikipedia.org/wiki/Blue_chip_(stock_market)

There is not specification to classify which one is blue chip, which one is not.

It is just a term being used to describe primarily on large cap and steady stocks. General low cap stocks won't be classified as blue chips, just like 'blue chips' in casino as posted, it refers to higher chip value one.

Hope it clear enough.

Feel free to further post in respective existing thread.

http://forum.lowyat.net/topic/864542
http://forum.lowyat.net/topic/851520/+2200