One of the easiest symptoms to fake is a cough. Everyone can cough and clear his throat on cue but you have to make sure your cough is convincing. Pretend cough may get you out of an embarrassing situation if the other person believes you are really coughing.
Practice your fake cough when you are alone. Open your mouth a little bit. Push out from the back of your mouth at the top of your throat. This will sound like a cough starting. Your stomach will tighten a little. You body will jerk slightly.
Continue. Push harder to make the cough louder and more real sounding. Your body will jerk harder with more effort put into the cough. Look at yourself in a mirror while you pretend to cough. Notice how your face looks. If possible, use a full-length mirror so you can see how your body moves and shakes while you cough.
Hear what it sounds like. Make sure it sounds real. Get a friend you trust to tell you if your fake cough sounds real. Use your pretend cough.
Cough once or twice. Stop the pretend cough. Now cough again more times. Make sure this simulates an actual coughing bout.
Fake your cough using something that will actually stimulate cough. Drink orange or grapefruit juice with pulp in it and swallow the pulp. This will irritate your esophagus and make you cough and choke for better effect.
Initiate a fake coughing spasm. Swallow and breathe in air at the same time. This is akin to "going down the wrong pipe."
Spit out the drink that you swallowed. Cough and gasp for breath. Continue your pretend cough until you the other person notices.