Find your falsetto by relaxing your throat and vocal cords, then squealing. To relax the vocal cords, yawn several times. Hold the pitch of the squeal, then add musical tone to it.
Sing a note you are comfortable singing with your head voice, then shift to the same note one octave up. Go back and forth between the notes to train your voice in how to access your falsetto comfortably.
Inhale, breathing with your diaphragm, to hold the falsetto notes. Picture your stomach as a balloon, and concentrate on filling the "balloon" with more air than usual as you inhale. Raise your eyebrows as you sing to increase your diaphragm control. Breath control is particularly important in falsetto singing, so work on your breathing techniques will pay off.
Visualize the air coming up from your diaphragm as you sing in falsetto, but let your visualization skip past your vocal cords. Focus on your upper throat, not on your larynx, since only the very edges of your vocal cords are used in producing falsetto. If you concentrate on your upper throat, your voice will be produced at the right spot in your throat and you will be able to hit even higher notes.
Place your hand on your chest to confirm that you are singing in falsetto. No chest vibration is required for falsetto, so if you feel vibration in your chest, you are still singing within your head register and haven't hit your falsetto yet.
Work on developing the high notes of your falsetto first, starting with the G above middle C. Lower falsetto notes, which are closer to and overlap with your head voice, are much more difficult to produce, so start high and work your way down.
Sing scales in falsetto, concentrating on producing as full a tone as possible. Practice all types of songs, from gentle, tender pieces to rock power ballads, so as to develop true versatility with your falsetto. Once you can transition from your head voice to your falsetto easily, sing scales that overlap the two types of voice. You can safely practice up to 30 minutes a day.