Flatten one end of straw. Cut off sides to form a "V", starting 1 cm from end. To avoid injury: Do not make the "V" sharp, and remain seated while playing the instrument. Blow through cut end, lips just covering entire "V". Slowly purse lips over straw, flattening the V until it buzzes on your lips. This is the tricky part.
Experiment. Can you change the tone by changing your mouth? What happens when you "tongue" the straw (touch the end with your tongue while blowing)? Place straw inside a plugged paper towel roll or vacuum cleaner hose. Flare the bottom of the straw and add another straw. Carefully cut holes in the straw and alternate covering them with your fingers.