Systematic Method of Chanting OM

The OM is to be chanted in a most comfortable posture.
The OM is to be chanted during exhalation after deep inhalation.
The OM is composed of two vowels A,U & one alphabet M.
The total timing of 10 seconds for chanting of one AUM is divided as follows:
A - 2 seconds

U - 3 seconds

M - 5 seconds

A - is to be pronounced for 2 seconds with open lips (about 6 mm).
U - is to be pronounced for 3 seconds while partially closing the lips.
M - is to be pronounced for 5 seconds while lips completely closed.
Complete 1 repetition of AUM is as follows.

1. Deep inhalation in 5 seconds.

2. Exhaling pronounce A for 2 seconds     with lips open.

3. Exhaling pronounce U for 3 seconds     with lips partially closed.

4. Exhaling pronounce M for 5 seconds     with lips completely closed.

This complete repetition takes 15 seconds and it can be repeated for as many times as you want.
You may find it difficult to inhale in 5 seconds and exhale in 10 seconds initially, so you have to adjust the timing as per your capacity in the beginning. But keep in mind that you have to achieve the ideal timings. If you follow the instructions given in the practice session, you'll be able to chant AUM properly and get all the benefits of AUM.