Just a little reminder Diolma, plop-render is your friend! It works great for getting an idea how changes will affect(and effect) a scene. You can just select a small piece of screen to render. I use the "spray-can" a lot too. It really comes in handy when positioning stuff like trees, rocks,people etc. when you're not sure they'll be visible in a render, or the little preview window doesn't show them.