Hi - good questions.

I use 2d high/low daily for my winning trades.
Yes I trade gaps.
I use both market and limit for entries, depending on the spread of the stock, and market exits.
Both NASDAQ/NYSE stocks are ones I trade.
Premarket volume is important, I cover specifics in my courses.
Here's a screencap of 2 widescreen monitors:
http://dtu1.com/2monitors.gif
See "Industry" listings at bigcharts.com for what stocks are in what sectors.

-Ken