Sometimes depending on my emotional state of mind I can make myself cry, especially during fights with my boyfriend. I start thinking about how I was wronged and deceived and fucked over in the past and I can "will" myself to feel those emotions again and cry more, but I can't do it all the time. Sometimes I will "will" myself to cry more so I get more sympathy during a fight
I think I could be a good actress but I need to learn how to "tap" those emotions on call, I can't do it yet, I can do it bette when I'm in an emotional state of mind.
Sometimes I used to fantasize about certain things (like daydreams) and would get so immersed in the character that I can feel everything that I as a character would feel, and I could make myself cry too. If you do it a lot it can be emotionally draining, but it can be cathartic too.
I think in some acting schools that's what they make you do. You have to think of unpleasant things that happened in your life and call on those emotions and pretend you're feeling those feelings all over again to make yourself cry, I think that's called "method acting".