How do you make an indoor cat become an outdoor cat?

There are many ways to help your cat become more comfortable outside. Think it through carefully before you go this route. Has your cat had all of his shots? Has he been around noises that are common to the outdoors (hearing birds and cars through windows isn't the same to them as it is to hear it without a noise barrier like a wall, door or window). Also, be aware that the cat may decide to become a predominantly outdoor cat which can result in no end of crying when he doesn't come home at night or when the cat wants to go out in the middle of the night to roam. If you still want to bring him outdoors you need to do this in graduated steps. First, take your cat out in the earlier part of the day when there are not a lot of noises around. If it is before the sun has risen he may feel more comfortable. He will still want to hang onto you, but you can slowly crouch or squat and pick up a piece of grass for him to smell. Let him see the outdoors one step at a time. This will make the transition easier. Try not to take him outside for more than a minute or two for the first few visits; he'll let you know when he is ready to progress to the next step by being reluctant to move toward the door or by getting on the ground and investigating. Remember that noise and fast motion will always cause your indoor kitty to seek the one thing he knows will protect him - you. Understand his cries are 'mommy - help I'm afraid'. Listen to his moods and the two of you may have occasional outdoor outings together.

try taking him/her out for walks or bring him along when you are going to your neighbours place who have cats so that the cats can 'communicate'.

Why would you even want to do that? First consider a few factors about your area... do you live on a busy street? Are there predators such as coyotes? Are neighbors going to be upset if your cat is pooping in their planters etc.? Out here, we have coyotes and people will move in, keep the cat inside for a couple weeks, then let it out. Then put up a poster for their missing cat. If I know who it is when they first let the cat out, I'll tell them. But most people don't care or don't believe their cat will be eaten. We have no cats around here. On the plus side to that, outdoor cats were often a nuisance where I used to live. One of the neighbors would go outside and shoot them. Others put out poison. We didn't, but I always remember finding cat poop in our garden and in our sandbox. I hated that people would have outside cats. Keep the cat indoors where he is safe.

Try to bring him out as often as possible, and wait until he is comfortable to go down and explore. Cats are naturally inquisitive but you can't force them into a surrounding that they are not familiar with. Like my outdoor cat Purr, he knows that he isn't allowed inside the house but there are times that I leave the door open. If I bring him inside, he would scramble to go out. But if I leave him be, he would start sniffing around and explore the kitchen. He looks cute with those perked ears, wide eyes with an expression, "Can I come in?" Lol. Give your cat time.