Being able to sing higher notes is largely dependent on whether or not you are doing your vocal warm up exercises daily.
So if you want to learn how to sing high notes I have just given you one of the secrets in the first sentence. Singing high notes is based on several factors but none are quite as important as doing the hard work of daily vocal exercises. I am going to give you a couple of quicker ways to get there, but nothing will ever replace the need to continue doing your vocal exercises.
The best way I know to sing higher notes has to do with the combination of voice exercises and lip trills. If you do not know what lips trills are let me give you a run down of how to do them. If you take two finger and place them on either side of your cheeks about one half an inch from your mouth where you can feel your teeth through your cheeks then blow, that is how you do lip trills. Make sure that your lips are not tight but nice and supple and relaxed so that they flap easily.
Okay so now that you know how to do lip trills you need to start doing vocal exercises on any scale and start working higher up into your range. Once you get to the place where you are having a hard time hitting the note without strain, bend at the waist and watch how you can hit higher notes more easily and without strain.
This is a trick that the pros use to sing higher notes because once you are able to hit these notes when bending at the waist they become easier to hit when you are not bending at the waist due to muscles memory.
Another way to hit higher notes with less strain is to sing your vocal exercise scale with staccato notes instead of legato notes at first. This just means that you use short and disconnected bursts of air rather than notes that are melodic and strung together.
Doing these notes first in staccato allows you to hit higher notes more quickly and like the bending at the waist trick you will build muscle memory that will allow you to sing these higher notes within a short period of time without the crutch of bending at the waist or singing staccato notes.
With preparation of you songs and with this new way of singing higher notes, you will have the confidence to step foot onto stage with less anxiety and far less stage fright.