01. Know your purpose before you startWhen you're thinking about how to design a brochure, start by asking clients why they think that they need a brochure. Then, they need to define their objectives. Sometimes they just want one because their last brochure didn't work. If they've come up with a brief for you, take a step back from that and look at exactly what it is they're trying to achieve.
02. Limit your fontsYou don't need many fonts when you're thinking of how to design a brochure - just a heading, subheading and body copy font. But we see it all the time in student portfolios - people think they need to find a headline font nobody has ever used before. Clients will usually take the lead on fonts as they'll often have a corporate identity in place.
03. Take stock of your paper stockTalk about paper stock before you put pen to notepad, let alone go as far as switching on your computer. If you're working for a client, ask if it has to be the standard A4. Find out if they've considered using uncoated paper, for example. there a great post here on making a paper choice.
04. Get your copy rightGreat copy is often the most undervalued element in brochure design. A lot of people don't understand that copy needs to be considered as part of the overall design concept.
At the early stage of any brochure design project, experiment with the copy to see if it needs reworking. Headlines aren't something to just drop in later. Here's a great copy writing guide.