3doutlaw's advice is spot on ...

Render settings + light settings + material settings = render quality (technically at least). It's the number of different variables, options and how they combine that can make things tricky.  IMO persistence is the most important quality for 3d!

There are a couple of pdf's in my free stuff - not tutorials as there are many other ways of approaching rendering etc (and some of them will be better) - but some of the info might be useful. Eg. the default render settings are not great, far better to get into the manual tab and learn about the effects of the different options - in the long run you'll get better results faster.

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