The intent of this thread is not be an end all, be all yeast dissertation but rather a primer with a few useful links and some information to help you understand the importance of pitching the proper amount of yeast. I also hope others will add additional information to this thread.

A friend of mine is getting ready to start brewing and he asked what is the one piece of advice outside of the normal "RDWHAB" and "Have good sanitation". After I thought about it for a few minutes I decided that proper yeast pitching is one critical piece of brewing technique no one told me about and I had to discover on my own through reading.

There are many benefits to pitching a proper amount of yeast and I suggest you read up using the books and articles available on the internet. The most useful for me being Mr. Malty's article on "Proper Yeast Pitching Rates" found here: http://www.mrmalty.com/pitching.php There is also a useful calculator and a yeast strain chart found here on Mr. Malty: http://www.mrmalty.com/yeast-tools.php

A few of the obvious benefits to proper yeast pitching include:
1. Faster start to fermentation. This is important because your young beer is most at risk during that period of time from when you bring your beer off of the boil and when fermentation begins. Before I pitched a properly sized starter I would sometimes have a lag in the start of fermentation of 24 hours or more. When I started pitching a proper starter I usually see the beginnings of fermentation start in about 6 hours.
2. In higher gravity beers if too little yeast is pitched the yeast can become stressed and put off undesirable esters giving your beer an off-flavor. I will say there are beers where this may be a desired trait such as Saison’s which are known for a funky taste.
3. Full Attenuation may not be achieved without the proper amount of yeast cells. If the yeast becomes to stressed they may stop eating the sugars and stop fermenting.
4. Cost reduction. Very simply, if you are using liquid yeast then you know the cost of liquid yeast. Higher gravity beers may require 2, 3 or 4 vials of yeast. With a starter you can reduce the # of vials you need to purchase usually by ½

I know there are more benefits that I am not thinking of so please feel free to add your advice.