A few more tricks.

Now that you have the hang of training feel free to try yet another trick.
To have the dog lay down, have him sit first.
Once he is sitting, place the treat near his nose and then draw your hand down towards the floor and then once he is lying down, state the command "Lie Down"

Once he can do this by command include a hand command.  You could simply point to the ground and say down instead of lie down.  There is no correct gesture and it is up to you to use one that will work for you.  If you are training a herding dog or a bird dog, I recommend you find books or sites that will teach you all the whistles and gestures that get the dog to work best in that situation.

This site is more designed for the urban dweller who has a small to medium sized dog that is not about to be shown or used for anything other than a family pet.

Once the dog can lie down you can use the same action with the treat and place the treat near his/her nose and draw the treat towards you and say "Crawl".  as he crawls towards you reward him.  Increase your distance from the dog and continue the process.

Rolling over is quite simple after the dog is trained to lie down.

Place the treat near him and say roll over and move the treat in a circular motion.  You may have to roll him over manually the first few times before he/she catches on.

Remember that these tricks are done individually over a period of weeks.  Take your time.  Do not confuse the dog with too many tricks in a day.  Patience, persistence, praise and love is all you need to succeed.