Something physical
Hide your face behind a big coffee mug, take a sip of whatever liquid and try and taste the flavor of every molecule in your mouth.
Take the stairs two at a time. Keep going up and up until your legs are burning so much that you now longer care about whatever was on your mind.
Dig your finger nails into your skin discreetly of course, drawing blood if necessary.
Concentrate on relaxing your facial features.
Stay busy
Talk to someone who is extremely analytical and non emotional, about frivolous things such as the postage meter or a message left earlier from so and so.
Try and remember tidbits of information useless facts trivia anything you have forgotten.
Analyze something- anything- like all the different techniques people use to keep from crying.