Pavarotti used a particular exercise to help him build and maintain core strength in his voice box when singing.
It is the simplest of exercises and one you can do safely by yourself without stressing your voice or overdoing it.
The exercise also features in my guide book and is one i use myself to help me hit higher notes.
The exercise is called the "Cuperto" and is formed on the italian 'u' vowel sound.
The 'u' sound (as in b-oo-t) helps to 'bridge' making it easier to move between your chest and head without breaking (flipping)
It also, alters the shape of the larynx to allow for higher notes without straining and reaching.
This tip is so easy i encourage you to try i at home. Here's how:
1. warm up (lip/ tongue trills etc). Once warmed up properly, do this next...
2. Vocalise on b-oo-t, GENTLY and SOFTLY. Focusing on the 'oo', siren up in to the head then down to your chest, then back to the middle.
3. Do the slide again on b-oo-t, this time THINKING about 'uh' as you do it.
That's it!!! Simple.practice until the 'breaks' begin to smooth out.
Once this happens you are on the way to 'bridging', keeping your voice connected into a higher pitch. Of course, there are more layers to this exercise which are better taught 1-2-1 but it will get you started.
In the meanwhile here is a video of Pavarotti, taking about his warm up routine.
To your vocal success