Just wanted to jog the ol' Grey Matter on the types of glasses available to the average pub patron. This will, in the end, help you choose a fine establishment to fritter away the day.
First, you have the normal, "American-style" pint glass. This is what you are served in your typical, "Joe sixpack" sports bar. These are generally 16 to 20oz depending on where you go.
Next you have the "Tulip-style" Guiness glass. Usually a 20oz-er, the majority of decent bars in this fair city use this glass for regular ales. This is usually available at the same type bars as it's American cousin, as well as the upper echelon that we will discuss next.
Finally (and I'm not going to get into the stylized, specialized, brand-specific glasses), we have the "English-style", Imperial pint glass.
This glass is special for several reasons. First of all, historically, it is a unit of measurement that harkens back to colonial days, when these units were royally sanctioned to the commonwealth. The King at some point changed it from 16 to 20oz. History plus booze is always good. Secondly, this unit of measure is 20 ounces, whereas an american pint is 16 ounces. In this economy more for less is better.
You can tell a fine establishment that cares about the proper way to serve a beer if these are the glasses they use. Thus, this blog.