How do you reset the check engine light on a 2003 Toyota Camry?

The best way:

Take it to your local retail auto parts store. Most of these stores will plug in their scan tool and tell you what turned on the light.

If it is something that just needs to be reset they can do that also.

If it is something that will just turn the light back on they will tell what the code says, you will have to get the problem fixed so the light will go out.