Stance angles

Just bought my own board after renting a few. Reading on the web, most sites
say that most people use forward andles for both feet. I think they suggest
starting with angles of around +20, +3.

I was looking at out local indoor snow centre (www.xscape.co.uk) and I
noticed that just about everyone was using 'duck' footing. I looked at the
board I was hiring and it was something like +20, -15.

Now I gues the only real answer is to try different angles out until I find
one that suits; but as I still consider myself a beginner it would be all
too easy to ick up some bad habits. So I guess the question is, how should I
make a descsion?

BTW, I have about 6 hours snowboarding experience, I can turn both ways but
I still fall over occasionally. As I said, beginner, but maybe not absolute
beginner.

Thanks
Dean