Stir frying is a cooking technique introduced by Chinese cooks and chefs. It involves rapid cooking (frying) in a small amount of oil and the use of a special cookware known as a wok. You could think of stir frying as what western chefs do when sautéing. However, sautéing and Chinese stir frying are different.
Have everything ready before you start
The first tip for making a stir fry meal is to have everything ready before you start the actual stir fry in the wok. You will need to chop everything beforehand. You will not have time to chop as you cook in the wok since stir frying involves rapid cooking at high temperatures. You will need to chop your ingredients into bite-sized pieces. For example, mushrooms may be cut in quarters, potatoes as julienne (small), etc. Pieces should be small enough to cook without burning.
Heat your wok before adding anything
Stir frying involves high temperature cooking (frying) so preheat your wok. Then add oil making sure it is enough to cover the surface of the wok. Then proceed to cook garlic, onions and herbs before adding other ingredients (just a couple of minutes).
Add Ingredients
Determine which ingredients will need more time to cook. These should be added first. For example tofu and carrots need more time than broccoli florets, red or green peppers and mushrooms, so add carrots, cook to 2/3 of time (approximate) and then add another ingredient. Keep stirring as you cook.
Add Sauce
When the last ingredient has been cooked you are ready to add any sauce if you like. Many recipes for stir fry call for adding a soy sauce at the end of the stir frying process. A sauce made of soy sauce, lime juice, rice vinegar and ginger is a great one. Add it to your wok and let it cook off. If you want a preparation that is more consistent (for example to serve over rice) add some cornstarch or flour to thicken the preparation.