Over the years, I have learned to appreciate the importance of simplicity and the power of the single portrait. Less clutter, more symmetry. One of the basic rules in photography applies to wall displays: a successful "image" keeps the eye moving in a circular fashion, has enough eye-catching elements to make full use of the frame, and has lines and angles that are always straight and balanced.
At the studio, we make use of a wonderful program called ProSelect, which allows us to take actual photos of our clients' homes, and drop in to-scale portraits (in their actual frames!) to make a digital "blueprint" of the layout. While this is certainly convenient on a commercial basis, it is not accessible to everyone. A nice computer program might be helpful, but creativity and determination also go a long way.
For a good starting point, I found a wonderful website article by interior designers SAS Interiors detailing potential photo layouts for beginners, full of diagrams and photographs. My approach always begins with selecting the place where the photographs will be displayed FIRST. The layout will have a lot to do with which images make the final cut. This is also a good way to make your final selections if you are having trouble choosing from a large group of images that you want to display.
Of course, the layout is usually quite dependent on what you want to afford. I like to have the prices of a variety of frames on hand while selecting a particular layout. IKEA has been producing some pretty wonderful frames as of late, and at very agreeable prices. While it's always best to see the frames in person, the Internet catalogue at least provides prices and is a good start. I generally recommend sticking with non-nonsense frames, black or brown, so the frames will "age" better. I try to avoid trends (like white frames and in other non-conventional colors) because I consider my wall displays to be an investment that I wouldn't want to change often. Crate & Barrel is another one of my favorites; more upscale but the frames are wonderful for smaller arrangements, and they also sell small shelves that match their frames, for a propped-photo type of display. On that note, I also like collect Crate & Barrel catalogues and tear out the photos displays for future reference. (An Interior Design workbook is a topic for another day, but everyone should have one!)
Another thing I try to remember if I like a particular layout of larger frames, but am concerned about the price of the photos, is that the frames don't necessarily need to be filled only with photos, but can also contain children's artwork, or perhaps coordinating and colorful fabrics, such as those designed by Marimekko. If you don't like online ordering, Marimekko is also sold by Crate & Barrel, their corporate offspring CB2, and in limited form at IKEA.
Once the layout is decided, I usually realize that through the process I have subconsciously already made a few photo selections for the layout. The thing to remember is this: don't get held up on one particular photo if it just simply won't look good with other selections. It follows one of my life mottos, which is "kill your darlings," which stems from writing advice by William Faulkner, but I believe that what applies to passionate and creative writing applies to most any other creative endeavors in life. Therefore, remember to think about HARMONY, FLOW and COLOR when selecting your images. Choose images from the same photo session, or if in doubt, go all black and white (not to say that a mix of color and black and white is not acceptable, in reality it can be really harmonious).
Lastly, a word on printing your images: this is where you should not skimp. It pays off to use the services of a professional photography printer. If you are printing yourself, find a local studio that guarantees acid-free paper and printing. There are also a great many places online that do a fantastic job, and it's worth a look at them. Most require a commercial contract, but if you are planning on printing often, this might be a good option for you. If you are printing through a photographer, make sure that they offer a lifetime guarantee on the printed images, acid-free paper, and professional digital printing. If you can select the option to mount the image on acid-free art board or some other sturdy base, do it. This way, the images will never buckle or bend from humidity and have less of a tendency of sticking to the glass.