Don't hang your art work too high. Don't overpower your rooms with art. Every room should have one wall that is free or art. Frames should be of the same material, such as golf, silver, wood, so they look cohesive. Don't mix frames of different finishes.
Group pictures together.
Avoid mixing mediums-oils, watercolors, drawings, photos. Like should be with like. Three items make a collection. Group like with like. Put the tallest items in back.