Throwing up can be very harmful to your health. The acid in vomit can eat away the lining of your throat so only do this if you have eaten something harmful to you. Each person has a gag reflux. To trigger your gag reflux you need to stimulate the epiglottis, which hangs from the top of your mouth at the back.
To make yourself throw up, you can gently put your finger down your throat. This is not recommended as it can cause esophageal damage. If you ate or drank something you shouldn't have, seeing a doctor is medically necessary.