For ORR, you could adjust your potential between 0 and 1.1 V vs. RHE. It depends also on the behavior of your electrode. some catalysts need more negative to be completely reduced like Ag. For RDE also you should notice the diffusion region.
As Juan suggests it depends on your experimental conditions, solvent, oxygen on your solvent, modification of your electrode, ect.
I think the best way is just to start with a small window using the solvent you will use in your later experiments. Then you broaden the window until you find the limits for your conditions.