Well, I can say how I render models; I don't know if more talented artists do the same, but I had some good results working this way.
First of all you need good-resolution models, for example: if you plan to render a vista you'll need some hi-resolution grass and ground cover. Actually it isn't so simple establishing if a model is an "HQ" one or not (surely Walli's ones are really good!
), but some factors such as number of poligons, MB or quality of the textures will help.
For what concernes the rendering I usually prefer set details between 0.65 - 0.85 (it depends on the scene) and AA between 5-7 and choose a filter such as Mitchell-Netravali or Catmull-Rom.
In this case in particular I've also sharpened a little bit the bottom of the image in GIMP (using alpha channels and two layers).
