When I saw the subject line here, I was wondering what Original Equipment Manufacturer had to do with e-cigs.

However, I'm sure the OP means ohms.
The lower the ohms (resistance), the more current you have going through the atomizer. Higher current results in a hotter coil and shorter battery life. What resistance you should use is really a subjective thing and you might find you prefer different resistances with different juices. There are charts that provide guidelines but, I've found they don't agree with my tastes.
Lastly, typical resistance for an atomizer is between 2.5 and 3.0 ohms. How far away from that range you can take it, depends on the battery you are using. For a cigarette sized battery, I wouldn't go below 2.0. I've seen people give the same advice on an eGo but, I'm not so sure you can't go lower. On mods that use generic batteries, you can put whatever you want on there.