Find a pond. Find dragonflies. Prefocus. Take lots of pictures. Practice. Eventually all the items will come together for a good shot.
Lots of shots that erer not so good. I'm glad this is not film!
I was trying to get a good shot of one of the maiting pairs in flight. They would pause (to lay egg) for a brief second and then take off. I pre-focused on the approximate position that I hoped they would be in, set lens to 60mm, F11, manual focus, ISO 200 and flash at 1/4 power. Handheld.