For daytrading you have to concentrate on very few stocks, for instance 5 to 10. Of course that does not mean that you can't change this set from day to day. Some day traders have there standard set, some others like to watch the current hot momentum stocks.

On the other hand there are traders who scan all day long the whole market with watching late breaking news or following daytrading room chat. There are even scanner programs sifting through thousands of stocks trying to catch entry signals all over the board minute for minute.

To take the idea of concentration to an extreme, select only one stock, which has a decent trend and fundamental growth potential and try to get on a long term trend with daytrading techniques, meaning apply a hard entry stop loss and try repeatedly.