Choosing and Preparing Your Tungsten

Tungsten plays a crucial role in the TIG welding process, which is why it is named after Tungsten. If you don't buy the correct tungsten; it won't weld correctly. If you don't sharpen it; it won't weld correctly. If you don't glob it (described later in this post); it won't weld correctly. Preparation and selection of your tungsten is a very important part of TIG welding.

Tungsten Thickness

Thickness is probably the most relaxed specification of TIG welding. Literally almost any thickness will work for a standard bead, you don't want the tungsten to be too thick because then it becomes harder to run a small puddle, and you don't want it to small otherwise the supposedly non consumable tungsten will start melting away, and ruin your tip. There is a small selection, and for small general purpose welds you can never go wrong with 1/8, 1/16 or 3/32. However, when going on very fine, or very thick metal, the thickness will need to decrease or increase respectively. 

• 1/25 - The smallest tungsten, used for very fine applications.
• 1/16 - \  These 3 sizes can almost be used
• 3/32 -  |  interchangeably, very versatile for
• 1/8   - /   nearly all medium sized welds.
• 5/32 - A bit heavier, unnecessary for general welds.
• 3/16 - Hobbyists probably won't encounter a 3/16, its fairly heavy.
• 1/4   - Largest common size, for huge metals and extremely high voltages.

Tungsten Color

WP - Pure Tungsten, completely undoped. The only function of this is AC, mainly being used on aluminum, it can also weld stainless steel and a select few other metals.
This tungsten is colored green.

WZr - Tungsten with added zirconium, this makes it pretty unstable for DC welds, but performs great in AC, The zirconium also stops the Tungsten from consuming with too high voltages, and protects the welds. 
This tungsten is colored white.
 
E3 - These are by far my recommendation of choice. Now this is no one-shoe fits all scenario, however it is excellent in a great number of fields. It can weld nearly every metal (aluminum, titanium, nickel, copper, magnesium, etc.) It is not specialized, it is solely general purpose. They outperform thoriated tungsten. However; many firms and individuals prefer thoriated tungsten simply because that is the tungsten they learned the art with. 
This tungsten is colored purple.
 
WCe 20 - Adding Cerium oxide to the tungsten increases the capacity. However, it is still outperformed by the E3, it is mainly used for lower/medium level voltages. This is somewhat outdated due since the E3 has come into play. 
This tungsten is colored gray

Preparing the tungsten
The procedure depends on the polarity and type of current you are sending through the tip. If it is DC Electrode Positive, you want a pointed tip, if it is on AC you want a balled (otherwise known as globbed) tip. Some people prefer a tapered tip, but I believe that process is completely useless and unnecessary, so lets get started. 

The first step in either process is to grind it down with a tungsten grinder. The reason I say the word tungsten grind is, you shouldn't use a regular grinder. If you use the same grinder you use for regular metal, you will embed the metal fragments into the tungsten, but it will do you if truly don't have another option. When you start grinding, you want all the grooves of the grind facing towards the tip, you want to slowly spin the tungsten forming a cone 2 and 1/2 times the diameter of the tip longwise. Here is a picture which will describe what I just covered: