In answering this question I am assuming that you already read through the 7 steps to start trading and the currency trading section of this website. After you do that and learn all of the basics, the first step is to decide what it is that you are going to day trade.
If you would have come to me a few years ago and asked me what you should day trade, I would have suggested stocks. Not anymore.
If you read throughout this website, you will notice that I have a preference for the forex market. One of the things that I like about it is that you can start with very little money. While you need at least $25,000 to day trade stocks by U.S. law, you can day trade currencies with a few hundred dollars. The automated systems page also provides a way for qualified traders to diversify their capital.