Question One: Do you want the shelves to be adjustable or stationary?
If they're to be adjustable:
A. Are you going to put those metal runners up the wall and support the shelves with brackets? (This is Mary's favorite, since it requires the least skill, sawing, drilling, etc.)
B. Do you want an enclosed space and put metal runners up the sides with clips to support the shelves? (This is what I usually use for bookshelves and kitchen cupboards.)
In this case, the shelves are NOT to be adjustable.
A. They might be connected directly to an upright board (Didn't make a drawing - That would be running the nail or screw directly through the upright into the shelf board.)
B. They might be connected to the wall, with a support underneath them. (I don't do this often, since it is the messiest looking finished job. But it supports the shelves well.)
This is essentially what I'm going to use for these shelves, since they will go all the way around the room at about six and a half feet up. The first pic here is just to show how these supports would normally look. You can imagine a triangular shelf across here, maybe four feet off the floor.
The second pic attempts to show you where these shelves are actually going, around a room in the attic, slanted walls on two sides. There will be two shelves, thus two rows of supports.