When cooking in a wok it is important that your pieces of food be small.  Also, using lean cuts of meat aides in preparation. Different ingredients require food to be chopped, diced, sliced(ex. peppers/onions) or shredded( ex. cabbage and spinach) because some foods cook faster than others.

Another thing to keep in mind is that being quick in your cooking technique is vital. Preparing the food so it is in small pieces, seasoning it, placing it in the wok and keeping it constantly moving at a high speed is the key to good stir fry. So, chop it up quickly, put it in , add soy sauce and other seasoning, and turn it swiftly and then enjoy it.