I always pick to be a stealth archer. I love thieving and I love assassination. It is a lot more versatile to be an archer than to just use knives. Finally, whats the best way to level archery? I just force myself to use it all the time. I'm currently at level 50 or 51.
Edit: If you want free steel arrows, there is a guy in the thieves guild cistern that constantly fires arrows at a target. I usually pick up 10-50 arrows per guild visit.