If you have a retail store, it can be really beneficial to develop relationships with your neighbors and help each other by combining your sales, events and outside displays. Just as a neighborhood street will get a lot more action if most of the neighbors have a garage sale the same day and call it a street sale, they will all get more opportunities which means more sales for each member.
If you're thinking of doing a sale, talk to the businesses around you and think of ways that you can work together. One way is to run one ad in the paper featuring both stores and split the cost equally. Four stores would split it four ways. This allows you to get a larger ad, or multiple ads in different sections for less than you would have paid by yourself.
Another way is to have attention grabbing things going on outside your store and split that cost with your neighbors. For example, a juggler, popcorn cart, musician, a band, demonstrations and so on. Make it fun and interesting to help drive traffic to your area and to each others store.
The less you look at other businesses as competitors and the more you look at them as creative partners, the better the opportunities for each of you become--even if you sell the same things.