Falsetto is described by some music educators as superhead or whistle voice. It creates a thin, yet bright sound that extends beyond the normal range.
Realize that there are two types of voices: head voice and chest voice. Everyone has both kinds. The chest voice is what we use when we're speaking, and is what males most often use, but to sing falsetto, your head voice is necessary. To use it you need to breath deeply from the diaphragm (to where your stomach goes out) and lift your eyebrows.
One of the most important tip I have found is.... Make yourself yawn or suck in air quickly. This lifts your soft pallet which helps you reach the note more easily.
Word of Advice: Do not try this without previous musical experience and an instructor