Two things that are the best things EVER we did with our two boys before they could go out was taught weeing on request and a solid recall. When we want to go out now with them in the car or leave them alone, i can take them out into the garden and ask them to wee and they do it, also poo if they need to, This means that I KNOW when they are in the car or shut indoors they are comfortable and not bursting. Their recall is amazing although I do say it myself and they aren't terrifically well behaved dogs. I used to carry a box of food around the house in my pocket, whistle for them from about age 8 or nine weeks (we got them age 7 weeks) and they would come for a treat. By the time they were allowed out (we live in the New Forest) they would come to my whistle (and later an acme thunderer for distance) with no hesitation. When adolescence came we had some recall wobbles but no major probs. and now at two and a half years old, (touching wood) the recall is rock solid again even with rabbits, deer ponies, cows and donkeys to distract them. I am not a great dog trainer, I jyst put the work in at the right time!!