Define and write down the conditions under which you'll enter a position. "Buy during uptrend" isn't specific enough. Something like this is much more specific and also testable: "Buy when price breaks above the upper trendline of a triangle pattern, where the triangle was preceded by an uptrend (at least one higher swing high and higher swing low before the triangle formed) on the two-minute chart in the first two hours of the trading day."
In addition to knowledge of basic trading procedures, day traders need to keep up on the latest stock market news and events that affect stocks—the Fed's interest rate plans, the economic outlook, etc. So do your homework. Make a wish list of stocks you'd like to trade and keep yourself informed about the selected companies and general markets. Scan business news and visit reliable financial websites.