true, watch the insiders' move.

which is a more effective way.

One thing I am not sure is "buy on rumors, sell on news". Once wathced a stock, up a lot in one month (guess people were buying on rumors), down 2% on the ER day before the release, after the earning release declaring good profit beating wall street expectation, jumped up by 10%. why did people not sell on news?

There are so many factors and all kinds of news: macro, micro, supplier, customer,ect...all are related and keep changing all the time,which can make the stock price of a company to fluctuate.