Tri-fold brochures are commonly used to provide more extensive information than a flyer. I have produced tri-folds as season overviews for Sacred Music Chorale, as well as for general information about the Greater Seattle Choral Consortium.
In general, my design philosophy on the brochures is to consider them in 4 parts:
The front panel should be visually compelling and should clearly state what the brochure is about. This panel is not about information, but is about inviting you to open it up and see what’s contained therein.
The back panel is usually looked at last, and should only provide tertiary information. This is a good place to put contact information, credits, or other non-essentials. Also note that if your brochure is designed for mailing, this is where the address information and postage goes, so leave room for that.
The “side” panel is the panel that you see when you open the front panel. It shouldn’t be too eye-catching because you don’t want to distract people from opening the whole thing, but it is a good place for secondary information or a more detailed look at something that is mentioned elsewhere.
The main spread is where the action is. This is where you need to balance the visual look and the information. It can be thought of as one giant spread, but you should still acknowledge where the folds are and use them to divide up your presentation. If you can logically break up what you want to say into three pieces, that is ideal.
For the visual element, find compelling photos to attach to each point you are making in the brochure. Move them around in the layout; allow them to bleed off the sides or go right up to the fold, or even across it. Once again, keep fonts simple; don’t overdo it with variants and sizes.
Here is a recent trifold brochure I designed. I generally go for 8½ × 14" (legal size) paper, which gives the panels a bit more room to breathe.