By positioning I mean where is it best to take the images from. For example from the side, rear or top down. The answer is that it is best to experiment.
Some species like the Skimmers and Darters point their wings forward while at rest. Top down shots are mostly ineffective in these circumstances, therefore a side view is best; however this creates depth of field issues, which can be challenging.
Most dragonflies perch in the cruxific position, these include the Chasers and Hawkers. Top down shots are the easiest in these circumstances but experiment with different angles, although you will have to accept a compromise on the depth of field.
Damselflies with the notable exception of the Emerald perch with their wings closed, parallel to their bodies. Side view shots are therefore the norm; however experiment with some really close up shots and you may be rewarded.