Once your puppy is old enough for basic obedience commands, you're going to teach him a few easy tricks first. Your puppy should know how to sit before you teach him how to lie down. Once he knows how to sit, the transition for the trick to lie down is pretty easy to make. Your puppy is energetic and eager to please you. He is at the age where training basic obedience tricks is still fun and not a whole lot of work for him.
Training your puppy to lie down will give you a great foundation for other tricks in the future as well as obedience expectations when it comes to behavioral problems. The 'down' position is a great way to have your dog wait patiently. So start training today so you and your puppy can begin to work on more difficult commands together.
To train your puppy to lie down you're going to have to teach him how to sit on command first. Decide before you start obedience training if you are going to use a clicker for all of your training sessions. If so, be sure to click train this position as well. Your puppy may start in a 'sit' position or go directly to a down position depending on your expectations of him. Your puppy should probably be at least 8 weeks old to begin training and preferably 12 to 16 weeks old before training beyond basic obedience commands. The younger your puppy, the more time it will take to train. Be sure to keep your little guy’s attention with short sessions and lots of rewards.
Be patient with your little guy and keep your training times short. If you are clicker training, be sure to have your clicker and lots of tasty treats on hand and ready to go for each training session. If you are not clicker training, have some treats ready for rewards. The basic obedience training can be completely reward-based and positive for your puppy, making all future training fun exciting and rewarding.