Not seeing “Bad, Bad, Bad” in a Becky thread title makes me cry.
Not an actor, but clearly the best acting involving tears has to come from someplace that hits an emotional nerve. Growing up, I had a lot of sad episodes, but was not able to cry on demand or anything remotely like that. After the birth of my son, however, something changed in me. Maybe it was hormones, I dunno, but “the waterworks” are a lot closer than they were in the past. For me the trigger can be beautiful music, especially if I have had a long association with that music.
For instance, in about 2010, I attended a performance at the Seattle Symphony where they played my favorite Mozart Piano concerto (#24). It was so perfect…it hit me like an ax. I was in a state of emotional shock and tears for at least 30 minutes. Nothing like that had ever happened to me before. I think I finally understood what the whole “crying at the opera” thing was about.
Check out Lennie Bernstein’s Mahler 6 on YouTube, where he is shedding tears during the heavenly* 3rd movement: https://www.youtube.com/watch?v=JMm5A2zf6hA (index to about 49 minutes in). His face is still wet by the time they start the spooky, tragic and overwhelming 4th movement.
It’s a talent, being able to function fully with the tears flowing. When this happens to me I am pretty much paralyzed.
*One idea behind this movement is that of a spirit leaving the Earth on its way to heaven, and being in Austria, on the way up it passes cows on the mountaintops. If you listen from about 41:30 you can hear the cow bells!
Sure. Just inwardly recite eight words.
No one was with Charlotte when she died.
I’d hate to think of how many nose hairs one would have to go through given that many scenes call for a Take 1, Take 2, Take 3…
That makes one of you.
You bastard! 
I think you’re on to something here, it was the same for me. When I was a kid, I would not cry in front of people. I didn’t want to, and so I controlled it. My family thought I was one cold-hearted brat.
Once my daughter was born, my cry-switch was broken. Any kind of emotional manipulation makes me well up now. (I still play it off so no one will know, but I have to do it a lot!)
She says I’m her One and Only! 
Et tu Brute?
(:))
In fact, Jackie Cooper titled his autobiographyPlease Don’t Shoot My Dog.
Tough town, Hollywood.
I vaguely remember either hearing or reading something from some actor saying that there was some breathing technique that they sometimes use to make their eyes water if they need to cry in a scene. Of course I can’t remember what it was now. And of course they still have to actually act to get the emotional part, but he made it sound like this technique was fairly reliable in producing tears.
Then there’s Washington, D.C.: Friend in Washington Magnet
Quite possibly, he was… acting.
(Friends and I often quote Lawrence Olivier. After Dustin Hoffmann explained that he’d stayed up all night to simulate “being on the edge” in Marathon Man, Sir Lawrence chuckled and said “My dear boy, why don’t you just try acting?”)
I can cry on purpose. I tense up my shoulders, and tighten my throat to produce the feeling of crying, then I imagine that “darkness descending” feeling I get when I’m genuinely sad.
For a long time I couldn’t cry even when I was really sad and wanted to, because my mother trained it out of me. She couldn’t stand the sound of children crying, and spanked me whenever I cried, until I stopped doing it.
In my early 30s, I decided I needed to learn to cry again (after going through my father’s death without ever crying).
I’d certainly cried a few times in the interim (not in front of my mother, though), and so I knew what it felt like, and worked on reproducing the physical feeling of crying, and then making the sounds and motions of sobbing on purpose.
Pretty soon it got to be that when something sad happened that made me want to cry, I’d jump-start it that way, and I’d be crying real tears pretty soon.
A few years later, I learned that I could actually cry even when there was no precipitating event just by going through the motions of it until it started for real. It takes about 30 to 45 seconds of pretending before I am bringing up real tears.
Thing is, once the crying starts, THEN I start to think of all the things I have to cry about, and it gets hard to stop sometimes. So I don’t do this very often. I’ve done it a few times to demonstrate that it’s possible, but usually I reserve it for times when I feel sad, but the tears aren’t coming naturally.
A British soap actress when asked about crying said she used a lot of tear stick and pulled faces. A quick google revealed that tear stick looks and works like chapstick but uses camphor and, you guessed it, menthol. Works for this young actor and like his mum says you don’t have to take a fan into the woods.
There was a Japanese game show that had a $10,000 prize if you could cry within 10 seconds. Some would just think sad thoughts, while others brought something to make them sad. The funniest was when people would bring photos of their idols. The idols weren’t sick or had passed away, but just thinking about them made some people cry, usually because they’d never meet them. Some contestants came close, but in the time I watched the show, this was the only challenge that went undefeated.
For me at least, that link doesn’t go that Mahler clip. It goes to the intro for the 1974 kids show Zoom, which I loved so thanks for that trip down memory lane. (None of the kids were crying.)
I always heard that actors could use glycerin for tears. Applied in the eye like a gel, which then warms and runs down the cheek like tears. Probably not good for copious crying, but maybe for that single tear that denotes such deep sadness.
There’s a quote I can’t find from a NYC mayor playing a role where they wanted him to cry - “30 years in politics, I don’t need an onion”