A trader can measure their performance as a percentage of the trading channel width. The perfect trade would be buying at the bottom channel line and selling at the top channel line, which would be a 100% performance. If a trader captured one-half of the channel, it would be a 50% performance. The goal is to continually increase the performance percentage of the average winning trade.
If the strategy is within your risk limit, then testing begins. Manually go through historical charts to find your entries, noting whether your stop loss or target would have been hit. Paper trade in this way for at least 50 to 100 trades, noting whether the strategy was profitable and if it meets your expectations. If it does, proceed to trading the strategy in a demo account in real time. If it's profitable over the course of two months or more in a simulated environment, proceed with day trading the strategy with real capital. If the strategy isn't profitable, start over.
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.