Odd wall last. Wrap the lighter paper round about half an inch or so, and that way you wont have any dark shadows down the corner.
Make sure you (might be stating the obvious here) paste the paper edge properly as this ensures that it sticks first time and doesn’t lift. Might sound obvious, but I have just re-papered the sister in laws hallway after a “pro” did it. Frankly with all his experience, I would have expected that A) his joints would be flat and, B) there would be no shiny bits where he rubbed the edge to death trying to flatten his poorly pasted edges.
Follow the instructions on how long to wait for the paste to sit on the paper before you hang it too, this stops shrinking. Use a new stanley blade to cut papers at top and bottom (and corners), and use a proper decorators scissors for nice cuts. Use the same scissors (edge) to push the paper in at the tops, bottoms and corners so the cuts are cleaner (Dont use the scissor to do the actual cuts though). Also – using your finger to push paper in means that sometimes when the paper is cut, gaps emerge – not nice.