Dr Joe suggests that the best time to meditate is when you wake up in the morning or right before you go to bed at night. During the day it is sometimes difficult to meditate because our brains are busy and often difficult to quiet down. 
 

However, the most important thing to remember is to meditate for at least 40 minutes every day, when you do so is really up to you.If you have not already done so, we would highly recommend that you read or listen to his book Breaking the Habit of Being Yourself and practice the companion Meditations. This book and meditations will lay a strong foundational understanding of Dr. Joe's teachings and meditation technique. 
 

In this book, Dr Joe goes into greater detail about when, where, how, and why to meditate. 
 

Below are the links for your convenience:

Breaking The Habit of Being Yourself Paperback Book
Breaking The Habit of Being Yourself Audio Book (11-CD Set)
Breaking The Habit of Being Yourself Audio Book (Download)Breaking The Habit of Being Yourself Meditation (Download)

We recommend viewing the following article:
Demystifying the Meditation Process