Many of the dragonflies I saw were flying around and not staying in one place long enough to be photographed. Sometimes one stays perched for long enough for me to get a few pictures.
I was about 4-5' from this dragonfly. I play it safe and get some pictures from my initial position before I try to get closer. Moving closer often spooks the insect and sometimes it just decides to move on. A 300mm lens (effectively 450mm with the DX crop factor) is very useful for getting useful shots which can be cropped to get further magnification.
From Heather Farm Park_06_23_11