Basics of Dow theory

The dow theory is the first theory made about stock market. It propagates to follow the market. It derives the trend by quantifying tops and bottoms as low and high. The line charts(daily) is used for dow theory. Minimum lookup period is 2 years. It is useful for monthly positioning and not for intra-day .
As per dow theory first we have to mark the tops and bottoms randomly and then qualify them as high and low. If there is a higher bottom to higher top supported by volume then the trend is bullish and if there is lower top to lower bottom supported by volume then the trend is bearish.
Using dow theory one needs to buy when there is a bullish trend and price goes above previous higher top and needs to sell when there is a bearish trend and price goes below the previous low bottom and the trend will be reliable for next 2 months.