The best source of day trading possibilities comes from the various gap up and gap down lists that are present on the net - for free.
I have three that I use. First I use a scan I generated on prophet.net. The scans there are free and scan real-time data. Only charting is delayed unless you have a subscription (I have a subscription). I also use a 1% excursion rather than take their 3% suggestion. I find 3% to be a large move and many times that is as far as the stock goes in the day.
Second I use the clearstation.etrade.com "tag and bag" section which has entries for gap up and gap down. If you go here you need to be early because the list can change though the day. Generally I hit prophet and clearstation before 10 A.M.
Sometimes I use data.inetats.com Toplist Top 20. Unfortunately this latter list will not be available for free after September 1st. No matter between clearstation and prophet there are more than sufficient opportunities for trades.
I discovered this method of trading (daytrading gaps) from another blog - Trader-X.blogspot.com
I've mentioned this before - Trader-X has forgotten more about trading than I ever knew and a few days on his site will give you a lifetime's education on how to spot setups and what to do with them once you do.
About the only thing I can add is that I use the VIX in my trading because I like its ability to confirm direction. Especially in a falling market. If I see the VIX top out and start to fall that is usually a good time to play gap downs.
In a rising market I use the setup to time the entry. When I see the "buy me" formation come up I generally pull the trigger.