When my 6 month old puppy is off lead she will come when called no problem... except when she has a ball, or toy, or pine cone in her mouth.  As soon as I throw the ball, she goes after it and then just runs round with it in her mouth. No amount of cajoling with treats will get her to come back to me. This goes on until she has run herself ragged, or eventually finds another distraction. I have tried waiting until she has been off lead for a while before we start playing and I also give her 5 minutes or so running around, before trying to recall her, but nothing works. Any ideas about what I'm doing wrong and  where I should start with training her how to play ball? Thanks

At the moment she has found a wonderful game where she gets all your attention for prolonged periods while driving you round the bend! :D  I think my suggestion would be to ignore her when she starts this, even avoid eye contact, then when she gets bored and drops the item, pick it up and praise her lavishly and give treats.  Also have you tried having two of her favourite items so you can entice her to drop one by offering the other?

I wonder if you're inadvertently training her to do this? It sounds as though it's become a lovely game - she gets all the attention and praise (do you say "Good girl" when you're trying to get her? - if so, you're praising her for what she's doing) for being a pain!

A couple of things you could try; have another toy to play swopsies with (you control the distraction!), or completely ignoring her till she comes back to you - no calling, no cajoling, no treats. Just stand still and be boring, not playing the 'catch me if you can' game that between you you've developed.

My Kody loves his ball more than anything and I have used it to my advantage. The ball is "Mine" not his, he only has when we go out. It is one on a rope and I started off by playing tug with it which most dogs love.  Then dropped it in front of him, he then started to run up to me for me to grab it which I do, dont try to take it off of him at this point, just play tug.  If he has  learnt the "Leave" command use it, I then take the ball swing it around a bit, I even tease him with it, then give it to him..it didnt take long at all for him to learn that he cant have this game on his own it takes two.  His ball is now his reward, he does all his training etc knowing that he is going to get his ball at the end.  He NEVER even looks at another dog while we are out as long as he has his ball, in fact he is never more than a few yards in front of me, especially if I have the ball in my pocket.  I started practitising this in the garden and believe me it is a God send. I do realise though that not all dogs have a High ball drive, fortunately mine does and it works a treat.!!!

Play the two hose/ball game.

The reason I mention hose is that it can be used as a tuggy and does not bounce erratically if you have a young dog which can lead to injuries.

If you are going to use balls then I would avoid tennis balls and use balls on a rope, if they have bells remove them.

Throw the ball out to the left as the dog picks it up and turns to you throw another ball to the right and keep repeating, this way you are always the centre of the game and the dog will always come back, gradually ask for more and more until the dog retrives to hand before you throw the other one, if you the dog goes off, just ignore the dog will soon stop as it is not having a game and you are not interested in it.