House Beautiful Magazine has a great series of tips from top decorators all about how to take your home from good to great.
We particularly like their tips for hanging art (above). See all of the tips - 101 in all - here. And, in case you're wondering, all ArtStar mats are 8 ply Hahnemuhle paper with a lovely beveled edge. For a great example of a gallery-style wall see below from Young House Love, and of course, you don't have to follow these (or any) decorating tips to the letter. The important this is to make your space your own!