Before hanging any art on a wall, try different combinations of arrangements. Use painter’s tape and brown paper bags and keep rearranging the bits of paper on the wall until you have come up with a great picture arrangement.
Always hang prints at eye level and use your hand in between pictures as a guide to space large and medium sized pictures.
Mirrors are great to help create the illusion of space. By cleverly placing mirrors on an adjacent wall to a picture or something which is interesting in your room, will reflect the image and add a sense of space.