The angle at which you position the camera depends on what features you wish to show and the species being photographed.
Taken from ground level, it shows the shape of the fungus and any features on the stalk, and, if you are lucky, the gills. For club and coral fungi, this is usually the best, but for agarics it's not the case as there are often details in the cap that can't be seen
From this angle, the cap of an agaric is shown off well, but gives you very little idea as to what it is you are looking at. This angle does work well for many of the cup fungi that don't have a stalk, or the woody bracket fungi that grow from the sides of dead trees.
At An Angle
This is the direction I chose most often for agarics showing both the cap and some of the stalk. It's still a bit of a compromise, as you are still not able to see the gills. or the top of the stalk.