Hiya,
If you use a water bowl, the placement should be determined by the humidity of your dragon's setup. If the humidity is incredibly low (<20%) you should consider placing it on the warm side, if the humidity is higher than that, place it on the cool side. If the humidity gets very high (>55%) the water bowl should be removed. Ideal humidity is about 30%.
Most dragons will not drink from standing water. I am lucky enough that my beardie - Guacamole - does drink from standing water. Instead, they get most of their
hydration from the food they eat. This is why a variety of healthy foods - fresh salads and gut loaded insects - is so important. Many beardies will also drink while taking a soak/
bath, but make sure to do this safely if you choose to
bathe at all (I personally do, 2-4 times a month).
Hope that helps,
-Ellen