We're getting there with our recall. Batty is just 5 months old (literally just )
Every time I say Batty, Come, and he comes he is rewarded - same thing for when I whistle. No matter what is going on or how frustrated I am he is rewarded like it's christmas.
He is learning that the word "Come" means race back to mum and something awesome will happen. Sometimes it's a rousing game of tug and wrestles, sometimes it's an awesome treat and sometimes it's to have a huge fuss made of him. Whichever I have handy at the time. It is imperative that you ALWAYS make it positive!
I also have two back ups. The first is "Hey Batty, Are you Hungies?" which is what I say to him just before sorting dinner out, and the second is Batty, Do you want a Treat??".