How should I introduce my cat to the great outdoors?

After 4 years - he is going to come back. However, there are some things to consider before encouraging him to go out. Once he starts going out regularly he will get fleas and probably worms too. So at least once every summer you will have to buy special drops to put on the back of his neck. Often best to get these from the vet (supermarket ones are not usually strong enough, and they are poison so you don't want to repeat them too often). Once he starts going further afield he could get run over. Depending on where you live he may be in danger from the wild life. Throughout most of the UK cats can be attacked and killed by foxes. This doesn't mean cats shouldn't be allowed out, just that it is advisable to keep them in over night and to have a cat flap for them during the day. So give some thought first to whether you want him to roam free, or to just go out with you, or to stay indoors. It is difficult to get a cat who has roamed free to understand why he can't go out at all times, so best not to allow this if you are going to change your mind later.