Welcome to Vue! :-)

The first thing I recommend is: watch tutorials and follow them. As many as you can. My favourite site for tutorials is www.geekatplay.com. They also have great materials for sale. In Renderosity there are also many. Watch as many as you can. I must have watched all on the Internet... :-)

And, as painful as it may be, I highly recommend you to read the Vue manual. I did.

Watch reference photos. There are millions on the internet.

You should try for yourself to discover the answers to questions you dont see in manuals and tutorials, before asking someone else. The best way to learn is when you discover it.

Regarding your particular image, here are just two pointers:
a) The mountains are not realistic. Practice with the terrain editor.
b) The shadows are too dark. In reality, in a sunny day, the shadows are not this dark. There are three basic ways of improving this: 1) slide the light sliders towards the ambient light, 2) increase the light from the sky, 3) double click on the sun and decrease the shadows (to 80%, for example). Or you can use a combination of all of these.

Have fun! :-)