Tip 6. Focus On Progression
As mentioned above, your workouts should really be under an hour if even that. But the main take home principle is to make sure you are progressing at a workout. It's so simply yet so many people screw it up. They put in more volume and more until their workouts are at about 2 hours.
Now some things to work for a while and you may see some results. But if you want to gain weight, you're better off focusing on progressing in either the number of reps or an increase in weight lifted within your main program. Just like overeating, this too will be tough and require you to push yourself to the limits.