Originally Posted by
DYKWIA
The first time you go through, go to a normal queue and ask to be registered for SmartGates. They'll do that for you there and then, and put a sticker on the back of your passport. Subsequently, you can just use the smart gates.
I haven't done this, but I read in the comment section of
an article about SmartGates on onemileatatime.com that you can sign up at the SmartGates. The commenter said to go to SmartGates and scan your passport as if you are already signed up. It will of course not work. You will be directed to an agent nearby who will sign you up. This saves waiting in line at regular immigration.
Again, I haven't done this, so I cannot vouch for it. The article is also several years old.