@WesternGuy - Noticed the underexposure too, was quite a dark and dingy day. I generally don't like using the flash so I just went with the best I could get, hopefully if they still look good I will try on a better day.
@dc2105 - hard to give tech info as everyones equipment and techniques differ.
Some basic setup tips for these:
Taken with a Canon 600d and the 18-55mm kit lens
Used a tripod, turned off image stabilization of the lens
Setup in shadow to avoid harsh sunlight
Used live view and magnification to focus
Used 2second timer release to avoid camera shake
Also did small adjustments in lightroom for a final polish.