Say I am walking down the street and I pass by someone else who is riding a unicycle. What can I do to let them know I am one of their kind?
Or similarly, what should I look for when I am riding so I can tell other unicyclists apart from the civilians?
Say, “Where’s your other wheel?” If if they nod their head knowingly, you’ll know… 
Haha, that’s what I was going to suggest. It really seems to be the code.
Ask them to ride a b*ke. If they look awkward turning with handlebars, you know.
Well, motorcyclists have a secret wave depending on what kind of bike they ride. Maybe if you’re a muni rider, you turn three fingers down like an M, or something.
I’d suggest using the ASL sign for “unicycle”, but it’s pretty complicated, requires two hands, and basically means “a bike with one wheel”
I can’t figure out if you guys are joking or don’t understand the situation. If you are riding and a pedestrian says “Where’s your other wheel?”, why would you think the pedestrian is a unicyclist?
I would say your best bet is to comment on a detail that a non-unicyclist wouldn’t know.
Like…
“cool, is that a KH 24?”
“cool, a coker!”
“cool, muni rocks”
Prefacing with “cool” is clearly required. 
How about a more obscure approach: “Wow, another unicyclist! You are not the only one around here.” pointing to yourself.
Avoid using “I can do that.” I get that a lot, and 95% of the time it’s from people who know they can’t. Of those, 75% instantly change their tune if you stop and offer them a try. Of the rest, less than 33% are tall enough to fit on my unicycles, but it was their crude way of asking to give it a try.
Sorry I guess I miss read the scenario(s). I think “where’s your other wheel?” might be good to use between two unicyclists meeting up for the first time? ha ha.
In the scenario of this thread, if you’re walking and somebody is unicycling.
You could say, “I’ve got your other wheel!” or use any number of the common responses that YOU might use to respond to that annoying classic question, “where’s your other wheel?”
If you’re riding, then leave it up to them to tell you they ride.
Only those who experience shame require secrecy.
Privacy is for people who have something to hide?
MR has a secret salute.
I have yet to use it, but I know it just in case.
Maybe: “I’ve got your other wheel.” Add a knowing nod of the head, and you’re in business. Or they’ll just think you’re the one who stole their other unicycle. In either case, it could start a dialog.
I’d favor the 2nd option.
Rock on, gladiators!
Whenever I’ve seen another unicyclist (not that it’s been all that often, it must be said) I’ve imaginatively said “you’ve lost your other wheel!”. Only I say it in an ironic self deprecating way instead of a trying to be funny way. Obviously.
Someone came up to me a few weeks ago as I was putting the 36er away and he asked, “Is that a Schlumpf?” Turned out he wasn’t a unicyclist, just someone who’d heard of a Schlumpf.
In 22 years of unicycling, I’ve only once met another unicyclist unexpectedly whilst I was out riding, and he was someone I’d met a few weeks before and sold a unicycle to! As a bicyclist, I have never seen a unicycle being ridden. As a pedestrian, the only unicycles I’ve seen randomly have been performers.
However, I have sometimes speculated on how I would make myself known to a unicyclist, in the event that I should meet one while I am not riding a unicycle. I think I’d go for, “Excuse me, I’m a keen unicyclist too. Are you local?”
I said that? Oh, I see, you said that. I said
no words necessary - just do the Ali G (respek) snap
Best thing to do:
Just say: “Uau, I would like to try… Is that difficult?”
What happens next?
You will try, and then ride from ZERO segs of trainning… Who can do this? ONLY RIDERS!
Right?
I once saw a guy holding a Torker lx. I went up to him to talk to him about unicycling. He didn’t ride, didn’t want to and just handed it to me to keep! I’ve used that unicycle to teach two others to ride.
While up in Nova Scotia a couple years ago, I was standing in a parking lot, and a fellow ran up and shouted, “Is that a Coker!?” He claimed to be a rider, but like John Foss, I’m a little too tall for people to just hop on my unicycles and ride away.
The only other rider I’ve encountered as a stranger was Dan from www.thedan.com in Boston. His hook was a very cocky, “I can do that, you know…”
iv never even met another unicyclist other than the one that trained me and the 2 iv trained. =(