At or in front of the center of lift, which is the high point of the airfoil. NEVER behind; AT gives max. sensitivity--or even instability.  As you move forward toward the LE, you gain more and more stability, until the plane is so stable (noseheavy) it won't do anything but fly level. A good starting place is halfway between the LE and the high point.

Correct, or dissenting opinions?

--Ray

If you have no idea, it's a good rule of thumb to have the CG in front of the high point of the wing, depending on design. I had high aspect ratio planes that had the CG very, very far aft and flew pretty well, but that's an exception. If you put it in front of the high point to start, you will probably have something that won't be so unstable that it's unflyable. Having a CG too far aft can be, uh, thrilling on a first flight.

Here's a link that will allow you to figure where to place the CG for almost any wing planform.

http://adamone.rchomepage.com/index5.htm