[OSM-newbies] Is building=yes (or landuse=retail) necessary in addition to amenity=fuel?

[Sebastian Arcus]

I've been tagging recently some shops and fuel stations which are on 
their own (not part of another building or site), and I have some 
questions. If I tag them simply with amenity=fuel (or 
shop=garden_centre, for example), they only show up on the OSM map as a 
POI - not the entire area traced. However, the rendering works correctly 
if I add the tag building=yes (or landuse=retail, if it is an area of 
land, and not a specific building).

I just want to make sure I understand things correctly. Is this the 
right way to do things? Although tags such as amenity=fuel can be 
applied to entire ways, not just one waypoint, the extra tag such as 
building=yes or landuse=* is still necessary  in order for it to show up 
correctly on OSM's map (and presumably other renderers)? According to my 
experiments, it seems that is the case, but I want to make sure I'm not 
wrong.

On the other hand, is it preferable to just tag the building on its own, 
the are of land with landuse=* on its own, and then place a separate 
node in the middle with amenity=fuel? Or not?

I've been searching the OSM wiki, and the descriptions of various tags 
are great, but can't seem to find a page with best practice for things 
such as the above - although there might be one somewhere.

Hope the above makes sense.

Sebastian