How the P sound looks and how it is made:
The position of the tongue is low (but could change depending on the word), and the sound comes from the release of air once the lips are relaxed.
The feeling with this sound is that it is a popping sound, and the lips are used to hold air pressure in and release it in a sudden burst.
How the B sound looks and how it is made:
The lips coming together to obstruct the air in the mouth from escaping produce the sound. The tongue is position can be low and dependent on the word; the air pressure builds up in the mouth, and releases a sudden burst of sound along with vocal cord vibration. The feeling with this sound is that of the lips coming together, in a way that releases air to produce a sound that is vibrated in the vocal cords.
How the M sound looks and how it is made:
The production of the sound is through the lips rounding together pressed into each other, and obstructing the airflow. The tongue can be low, but is also dependent on the word. The nasal cavity is open and allows for acoustic sound through the nose. The vocal cords produce vibration for this sound. The feeling for this sound is in the lips, and the way they press together almost rolling inward.
Lipreading.org