There is an adjusting screw/bolt with a clamp nut on it on the choke rod.
I don't want anyone to think that what I say is exact. But, I have always followed the "no more than double your idle speed on choke" rule. Once again it depends on where you are in the world, your elevation, humidity, and temp. are all factors that you should consider.
That being said, I say no more than double your idle speed just for precaution. To me, I think that starting a cold engine with cold oil and cranking up the RPMs is just asking for trouble. (Once again, there are factors that can change your personal settings)
Now I only have a KZ550 LTD and a KZ750 Spectre, so on other bikes the idle speed and choke may be different. In that case I recomend having a manual, or finding out your bikes specs on the web.
But, I still believe that not much more than double the idle speed is the safest way to go.
If anyone has any more info, or has another opinion, I welcome it. No one man knows everything (but he can try)