Some things to consider:

Will it be printed on a digital machine or a full colour litho machine? If you are looking for quality nothing beats litho.

What material to print on? Weight, Stock, Texture

What size? A4, DL, A3.

How is it being folded and does it need creasing first to stop cracking.

What are the Contents and Images? It saves time and money to have all your content ready before you start the design process.

Do you have a look and feel in mind? Perhaps have a look around this will also give you more control of the final design.

Brochure design is just like web design, only when you make a mistake (and you will) you can't fix it after it has been printed.

Check carefully, then check again and then get other people to check for you.

Nothing beats experience.