Let me summarize what I understood. Most points have been iterated by plasmabhai earlier.

I shall talk w.r.t Karizma here.
1. Max torque @6k rpm
2. Max power @ 7k rpm
3. Every upshift reduces the tacho by 1.5k rpm

For best acceleration, upshift @ 7k-7.5k rpm, so that the next gear falls in the meaty range of max torque of around 5.5k - 6k rpm. But in practice this sometime leads to a power wheelie in 1st!
Note - this reduces engine life by a good extent.

To ensure proper engine life and keeping a balance between performance and mileage (and engine life), upshift @ 4-5 k rpm. Also, maintain a linear application of throttle.
Redlining once in a while helps in reducing carbon deposits, but they must be practiced 'once in a while'.