[mrg666]

What I generally do in manual shifting:

Upshift before the engine starts screaming if I don't want to accelerate more.
Downshift before I accelerate when the engine is not already revving.
Downshift to start revving before the curve if I want to exit accelerating. Downshift before uphill if I want to maintain or increase my speed.
Downshift sequentially while coming to a stop.

As the driving gets more aggressive, upshifts are done later and downshifts are done earlier at higher rpms. Or, upshifts are earlier and downshifts are later at lower rpms in casual driving. I just listen the engine instead of counting the gears.