In general, artwork should be hung so that the centre point of the picture or grouping is at about eye level for the average person.
While this won't be possible in every situation, it's a good guideline to keep in mind.

Another technique to remember is that a grouping of pictures should be thought of as one unit. Test an arrangement of pictures by laying everything out on a large table (or on the floor), playing with combinations until you hit upon one that works.

Laying them out on paper is even better since you'll be able to trace around each object and determine where picture hangers should be installed. Tape the paper up on the wall as a template for picture hangers and you'll be done in no time.

In general, when hanging art over a piece of furniture it should not be longer than the width of the furniture.
The artwork principle of being about 75% of the eg  table's width.

Choose smaller pictures for narrow walls and larger works for big wall spaces. Here a hall wall is accentuated by hanging a set of six prints in a tall vertical arrangement. One or two larger vertical pictures could have been another possibility for this space.

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