That's how we all start!

Practice Practice Practice.

Look through my renders to get an idea.  My very first render was June 2011.  I've come a long way since then.

 

Start Simple.  The first thing I did was read the Poser portrait tutorial, it really helped my learn about lighting.

Since then, I use Reality almost exclusively for my renders, and I found Paolo's tutorials ($20?) for Reality extremely helpful.

I spend most of my time on the forums asking questions about how people do what they do.  If they do something I'm interested in, I try to learn it.

 

And yes... some times I turn out some crap, and kinda walk away from it.