Best way to Manually Shift?

[svxthc]

When wanting to go fast, I enjoy shifting from 1 into 2 into 3 into D. Should I hold the gas pedal down while shifting around 6rpm or let off and shift into 2nd? When I let off the car chugs and the tranny hesitates and makes a loud bad bump noise. I'm guessing that I should just hold the gas down when manually changing gears in my automatic, right? Also, how bad is it to do this and race the car and how bad is it to hold the brakes on and the gas at the same time to get a faster start. This is in a controlled course. Thanks.