/ic/ - Artwork/Critique

So I started drawing earlier this Tuesday, and have been doing at least several drawings per day. I read the sticky, and have been studying Loomis. I'm focusing on Digital art, but I try to draw from life as well.
I feel like I picked on several things in the process:
1. Start at the background and work your way to the foreground.
2. Have a 'keystone' where everything else in the picture is drawn in relation to its position from it.
3. It's okay to draw things a little bit smaller, because (for example) a house drawn too big will take up more space than intended (although this just may be my lack of perspective).
How right/wrong are each of these? I'd hate to start developing into a method that's bad practice.