ok, this is going to sound heretical, but is trading your own account necessary at all ? Why do people insist on trading or stock investing when it is so difficult and time consuming and when there are perfectly good firms that you can farm this out to.
Stock selection : can be farmed out to funds (hedge, mutual, sector specific, strategic (eg small cap, bear)) funds. I believe I (and most individuals) have no selective advantage in stock selection over these entities.
Trading : can be farmed out also. I believe I have no selective advantage over proprietary trading firms. Why would I want to do this, it is like going to medical school so I can deliver my wifes baby. There are obstetricians who can do this so why not use them !
This leaves only two arenas in which the firms have no advantage and that is in market timing and asset allocation. Most funds have to deploy their assets, they cannot risk underperforming year on year. Their variation in cash is pretty miniscule (0-10%). So if I feel bearish then I can have more in cash. They also have portfolio allocations that are generally restricted in it's parameters (they cannot for instance go from being diversified to 100% property or shares). I see it as rational to employ their services to construct my own portfolio based on my risk preferences and investing experience. This makes the process of stock selection and trading redundant.
performance someone once told me is 90% portfolio asset allocation