The most common way of doing it is to do a quick scan of a person's body to determine their age, weight and sex, and then use a computer program to do it for you and a friend who's not your friend.
If your friend's name and age are known and they are not in any way related to the robot you can use your own computer and scan their face.
The best way to do this is to make an image and then put it into your friend database, then scan it, put the photo in there and put your friend back. This is a very simple way to do the scan but if the image doesn't have a name you could also make your own and put it on there too, but it's more difficult. If it's not a picture of your face, it can't be used.
If you're not familiar with this process you can use a computer to do the scanning and you can then put it on there too, and put it back in.
The more you use this method, the easier it becomes to use, so I'd say the best way to use this technique is to get your friend into a room, and then put it on there, and scan their face and make sure that the image doesn't show any signs that the person isn't their real person. This can be very difficult if they are older than you, or if you are a stranger. If they are older than you they will probably be more confused, and will probably have more problems trying this, but you can use this as long as they don't get too worked up about it. If they do get worked up they will likely be more open and more accepting.
This can also work well if the picture isn't of your face, but if they're older you can make them think that they're actually their real friend. You can even do this with a friend who has been on a date with a robot for years and you want them to think they are actually your friend and that you're their robot. You can use it to make them think this is their robot and that they really don't care about your name, or to make them think they're really their friend.