Author Dave Farland recently posted three rules for drawing emotions out of your reader (in this case tears.) I highly encourage you to check out his full post over on his blog. I particularly liked his first rule:
1) Protagonists don’t cry. If your protagonist does cry, then it frees the audience so that they don’t have to. Hence, if you’re trying to draw genuine tears from a reader, your characters shouldn’t be crying.
His whole “Kick in the Pants” series is really good. A must read for any aspiring authors.