know yourself
Start off, as with betting sports, by knowing yourself. Do you want day trading with all the shocks that can produce? Or do you want long term returns? Or somewhere in between?
Personally I haven't got the time to day trade. So I follow a value based, Buffet style approach. I hold between 8 and 15 stocks at any time and trade on average 7 or 8 times a year. Some stocks are core holdings and will never be sold unless they are badly mismanaged at some point.
It's boring but it's reliable. I started 8 years ago and have beat the market in 7 of them, on average by 6%. By taking slightly less risk than the market. I spend about 30 minutes a week on my stocks on average, mostly 0 minutes then a week or 2 of 1 hour or so when I am thinking of a trade or 2.
Much of my outperformance comes from paying hardly any dealing fees because I pick good stocks and rarely need to sell them. I'm not likely to be in the next Microsoft. But I am even less likely to be in the next Worldcom.
This may suit you, or it may not be exciting enough. Only you can decide what approach to take, there are many which work.