This article shows examples of a number of pull quote and block quote styles used around the web. Interesting to look at not because you should automatically do what most people do, but because you get a definite benefit out of adopting a style that people are already familiar with. Users don't need to relearn what something means if they've seen it before.

Of course, the style you use has to take into account the context of the implementation. (And the need to not offend the sensibilities of people with a more... critical view of grammatical niceties.)