Stock Trading

Anyone interested in the stock market knows what a trend is or at least should know what one is. I can look at charts and spot trends in numerous stocks and indices at any time. But how do we know what kind of trend it is? Is it a primary trend? Or is it a counter trend as defined by the wave theory? If a stock has recently bounced back from a new high or low, how do we know if this is the start of a new trend or just a bounce along the main trend?