Plaster a half-smile on your face. This is sort of the warm-up for the Tom Cruise laugh. When you are listening to someone else tell a joke or a story, look at them with a half smile already adorned across your face. This will give the precise amount of faux interest that Tom Cruise tends to sport before he laughs.
Break into a "shoot-eating" grin. Smile as wide as humanly possible as the story or joke comes to its culmination. Your face should physically hurt from the width of the smile.
Laugh with the back of your throat. The way Tom Cruise laughs is by exercising his glottal stop in the back of his throat (yes, it's an actual piece of the human anatomy.) When using your glottal stop it will feel as if a clam or piece of cheese is stuck in your throat as you laugh. Almost as if your airway has closed. Practice short bursts of sound. If you are a "Back to the Future" fan, Crispin Glover did this brilliantly as Marty McFly's father.
Lean back with your entire body. Tom Cruise doesn't just laugh, he commits to his laugh by getting his whole body into it. Lean back with your body as you guffaw with your glottal stop.
Pat the other person on the back. Tom Cruise also loves to physically share with other people (lucky them.) Make physical contact with the other person by slapping them on the back, or grabbing his shoulder.
Make eye contact with the other person. This isn't just a lesson in laughing like Tom Cruise, this is a lesson in life. People who make eye contact are more successful. Tom Cruise has mastered the art of always aintaining eye contact with the person in front of him.