Basic training sessions should begin as soon as your puppy has settled into his or her new home. Concentrate on one new command each week. Your puppy wants to make you happy and he/she will quickly do what you want, once he/she knows what is is that you want them to do!
A good time to start is at meal times with a simple sit command whilst holding the dog's dinner bowl. Start by holding a tasty morsel on his nose and raising your hand above his head, this will force his bottom downwards at the same time saying in a nice firm voice 'sit'. If he/she doesn't quite get the hang of it then whilst holding the treat in the right hand, assert a little pressure on his/her lower back with the other hand.
The command you give should be said in a commanding voice, maybe just slightly louder than normal, very authoritative but not too stern. "Sit!" means sit down right where you are and do it immediately. Saying a soft gentle "sit?" means please sit - that is, if you feel like it - okay, when you get around to it - maybe?
When he/she gets it right then give lots and lots of praise in a really happy sounding voice and give a treat as a reward. This is the beginning of getting your puppy to understand right from wrong.
By teaching this command a meal times it also starts the puppy to learn 'food manners'.