I also start out in second gear. I've only tried first gear a couple times, just to see how low it really it is. On the other hand, I don't have anything to tow yet.
When I was breaking in the truck I would occasionally give the motor some nice steady pulls up to 3,000 rpm in as many gears as conditions would allow. With 9,000 miles on the truck I feel that the motor still has some more breaking in to do so I try to mix up the driving and work the motor at different rpm's.
As for shift points, they go higher as the motor warms up. When it's cold, I short shift at 1500 to 1800 rpm. Once it's warmed up I generally shift in the 2200 to 2600 rpm range. On long trips I'll drop down from sixth to fifth just to mix it up. This usually puts the motor in the 2600 to 2800 rpm range at freeway speeds.
I still like to do steady pulls up to higher rpm's, sometimes pretty close to the redline on the tach (3250?) but only when I know everything (motor, transmission, differential) is completely warmed up.
One thing I've noticed about the 6 speed is it seems to shift a lot easier at higher engine rpm's. IMHO, it seems to shift the easiest around 2600 to 2700 rpm's.
I don't downshift too much, the transmission doesn't seem to like it unless you increase rpm's on the motor to match the new gear. Also, I know downshifting makes the synchro rings wear out faster. There's always the discussion about what's cheaper: brakes or transmissions. I tend to drive slower than most I guess and leave plenty of room for coasting to stops.
Waiting at lights, I'm generally in neutral with the clutch out. I've replaced throw-out bearings in several trucks over my lifetime and it's one project I can do without.
Gas mileage ranges from 18 to 22, hasn't really changed much since day one. I use a fuel additive occasionally, maybe every second or third fill up.