When arranging pictures on a wall, create the arrangement off the wall first until the spacing is idea. Have someone else hold the pictures against the wall to see how they look. Taking measurements before hanging them is a good tip.
If the arrangement includes multiple picture frames in one area, use a linking element. This could be that they are all from different family vacations or include photographs of all the kids from different ages and grades. Hang the pictures at eye level but don't be afraid to have some smaller pictures a little higher or lower, depending on how many pictures there are.