Below is an image from Better Homes and Gardens, and although I've never done it, I think its my favorite technique to hang pictures and I'll definitely be trying it in the future. There are many different methods you can find online, but this is the best tutorial at really being able to see how your art work will look on the wall in terms of spacing and balance before you start putting holes in your walls. You simply cut out pieces of paper to the size of your frames, and tape them up on the wall how you'd like to display them. If you don't like the way it looks, you just pull it down and try again. Once the pieces of paper are on the wall how you want them (make sure they are level!), measure the distance on your frame from the top, to the bracket where you hang the nail. Then mark the same distance on your paper, and nail right through it. And before you know it, you have a great looking wall grouping!