There are several things we need to consider before starting to design a brochure: the size, shape, and folding type besides the concept itself. Generally, we should start with pen and paper - literally. It's a good idea to grab a piece of paper and start looking for the best way to fold it, anyway at the end you'll have only two printable sides, that means, two Photoshop documents, one for the front side, and another for the back side.
This time I'll show you how to design a three-fold brochure. Below is a quick draft of the folding guide. From here and forward, we'll name each print area a "Face," so we have "Face 1," "Face 2," "Face 3"... until "Face 6."