I always lunge all of my horses before a class, I find they focus a lot better. It helps to get the unnecessary energy out that would normally distract them. Tiffany foster has talked about this a lot of you want to learn more about the benefits from a professional.
Hey!! I ride young horses so I lounge them a bit so they don't have lots of energy when I ride them! But as they start to be more confident and responding to me properly, I just work them a little by hand and then ride them! Hope it helps