Hey Duke-

Welcome! And thanks for your question.

I just posted this new revised tutorial on speeding up and smoothing out your chord changes (Seamless Chord Changes for Beginners), that might be helpful for you.

Here's the link: http://www.guitartricks.com/tutorial.php?input=484

This tutorial may help give you some strategies for making your chord changes more quickly and smoothly.

As to exactly WHEN to change from one chord to the next, that really varies depending on the song or piece you are working on. Give us a little more info and we'll try to be of help.

Best wishes - Lisa