I must be one of the lucky ones... I can cry upon command. The downside is that I get weepy at the most inopportune times... saying the Pledge of Allegiance, thinking about lost kittens, watching my children do anything. 

The ultimate goal is that you are so involved in what is happening that you do cry as the character would - but that doesn't always happen.

If you start to 'act' as if you are crying - shaking lip, tight mouth, sad expression in your eyes etc - it will just come.  SOemthing to do with muscle memory - your body remembers that the last time it was like that it produced tears and voila

I often have a problem with people who are too into the whole sense memory thing- they get so wrapped up in their "real emotion" that they stop paying attention to all the other stuff (like fellow actors).  It may be powerful to feel real grief and cry from that, but it's also distancing.

There's a careful balance to be struck between being too fake and too real.  I let myself be guided by the script- look at the way the lines are written- the pacing, phrasing, etc.  If you just let yourself get carried by the dialogue (and blocking), whatever happens or doesn't will tend to be appropriate, if not necessarily "real."

If you want to get really deep and use the Stanislavsky method then really you shouldn't need any tricks or tips -

You should be so into your character and into your given circumstance that the emotions naturally flow.

If you are having trouble with this then you use sensory recall or the 'magic if' - (what if this happened to me). 

Having said that - that's what I teach but personally I find it very hard to be that into a character - but I guess that's why I'm not on Broadway right now eh!

I've been staying out of this thread, mostly because I knew it would get to this:  Stanislavski vs. Strasberg vs. British systems vs. whatever the flavor of the month is.

And I don't get involved in religious discussions.

But I'll throw a couple of thoughts in now, since the argument has started anyway, and then I'll run away and watch the fireworks.

1) Sense memory is not used onstage.  Not. Not. Not.  It is an exercise.  Like any exercise, if it helps, use it, if not, don't.  But onstage, it is potentially dangerous, distracting, and worst of all, false.  Because your dog didn't die, dammit, Willie Loman did.

2)  Stanislavski explicitly said, over and over, that character building begins with the externals.  Actions, NOT feelings.  He said, and taught, that you must play only actions.  He wrote pages and pages about playing around in the costume shop to help himself look like Othello.  The fact that Strasberg taught something different in his name doesn't change that.

3) Magic If:  One of Stanislavski's pupils (Vakhtangov) put it this way:  "What would I have to do in order to do what the character does in these circumstances?"  Obviously, I don't get to do what I want to do in the circumstances; nobody wants to see a play about me anyway.    I am limited by the author's choices; my job as an actor is to justify them.

Willie's dead.  I'm at his gravesite.  Why am I there?  Why is he dead?  Is it my fault?  Is there something I could have said?  What do we do now?

If I place myself into these circumstances, and really think these thoughts, my reaction will be true to the playwright and to myself.  And if I don't bring actual make-the-costume-wet tears, well, maybe that's because I've spent so many years trying not to, that I can't right now.

But that doesn't mean I'm not crying.