I started doing this a few months ago and it has been a humbling experience. I have been able to make money, but have made more for the broker and nearly as much for Mr Darling as for myself. My biggest mistakes - 1) crap brokers 2) trading UK equities (stamp duty) 3) inadequate preparation.
My strategy - read the news, research actively from 0700-0755, trade 0800-0900 or until I have cleaned up the mess I made between those hours. Research for several hours in the evening.
But in today's market, how can you lose money? Oh, I remember, buy something just before it gets delisted.
Good luck!