If your dog reacts well on your command and he's all happy to get some reward after it's arrival, you can start to specialise the trick. You will help yourself with the reward (toy), which you keep in your hand in front of centre of your body, so that the arriving dog can see it well. With this reward you lead the animal on the centre of your body, with his forehead straight to you. If the dog has tendentions to go on the side, you make steps back so long, as the dog goes straight. The reward, which you still keep in your hand, you lift above the dog's head, which makes him sit. Of course, you can also add the command "sit down", or help yourself with the other hand, which you will catch the dog's collar under his neck and with small jerk up and towards you, you make the dog sit. Be sure, that the dog sits straight in front of you, without having it's front or back to the side (once the dog learns to sit bad, it's hard to make him to sit correctly later). Once the dog sits in the correct position, you must immediately praise him and reward him. This trick you should change few times with the trick "Free" (we will speak about this trick later, when we discuss calling the dog back when walking, with the command "to my leg !").
The last phase of the trick is to make the dog sit next to your leg. There are two ways how to do this - the older one, when the dog sits straight to your left leg (practically it "goes back") and second (taken from abroad), when the dog goes around you in the way of clocks and sits next to your left leg. It is up to you, which variant you are going to follow, but anyway, later you will learn to turn back, when the dog must follow you and always sit at your left leg.
To sit next to your leg you learn the dog that way, that you put him on the leash (it still sits in front of you), you give the command "to my leg" and with help of the leash you lead the dog to the requested position. At the older variant, you help yourself you're your left hand, with which you turn the dog towards your left leg. Your right hand with leash prevents the dog to move to the side and forward. Of course, after this follows big praise and reward. The whole and correct trick of dog's coming looks that way, that on one command "come here" ( you can use his name also) rapidly and straight runs to his master (who stays on one place), sits in front of him and on the next command "to my leg" sits on the left side of the master (of course without leash).
Beware of stereotypical manner - change the length of time, before you give the dog, who sits in front of you, the command "to my leg". The dog would learn soon to sit next to your leg without the command.

Helena