[barrkel]

Table aliases make queries much less verbose than using the full table name, and more readable as a result. Aliases are unavoidable when you're joining the table more than once. Not using qualified identifiers is just asking for trouble.

Short aliases - I tend to use the first letter of each word in the table name - work best, IMO.

[nickpeterson]

I tend to use two character because you might join similar named tables or the same table multiple times.