Clearing the throat in an aggressive way:

If mucus gets thick and sticky, it can be an irritation and you may feel the need to clear your throat by coughing. Unfortunately, this starts off a vicious circle whereby coughing may irritate the vocal cords and you will have to cough again and again to deal with the irritation. However, a lot of throat-clearing has nothing to do with excess mucus. 

The muscles in the throat can tighten, as a result of poor voice production or suppressed emotions, and give a feeling of wanting to clear something. Apart from dealing with the emotional causes, muscle tension can also be helped by exercises such as yawning.

Give yourself time to digest your food before singing. Quite frequently, singing on a full stomach is very uncomfortable and also increases your chances of acid influx in the throat. You can get medication for that but to avoid that happening, leave a long enough gap or eat after your performance.

PITCHING
All of us are blessed with our own natural ranges in which we function comfortably. However, if we use too high or too low a range, not only does it sound bad but the vocal mechanism cannot function efficiently and you experience difficulties. You may feel vocal fatigue, muscle tension, narrow pitch range, intonation problems and tone disturbances.