The secret to good shelves is not what you put on them. It is what you leave off.
Start with the big things
Place the largest objects first: a stack of books lying flat, a tall vase, a framed print leaning at the back. Then fill in with smaller pieces in groups of three.
Leave a third empty
Empty space is part of the composition. It lets each object be seen, and gives the shelf room to change with the seasons.
Group in threes, vary the heights, and stop before you think you should.
