A good brief will help you compare alternative web developers on an equal basis, and give your chosen supplier more opportunity to get involved. Here's a few ideas on what to include in your web design brief:
The more your suppliers know about your company, the more value they can add to the process, and you could learn a lot from the suppliers you don't actually use. Don't just talk about the cold numbers or lists of your business, but try to be more descriptive: Who is your typical customer? What are your values and passions? Why does your business exist? How do you want people to remember you?
Set some goals
Think about what you really want to achieve with your new website. What result would tell you that it's worked? Do you want to save time, or get more visitors, or just have a more professional design? What are the main actions you want users to take? How many enquiries, or sales, or visitors do you want?
Think about the users
It's easy to lose sight of the people using your site when you're seduced by great design or all the features your website could have. What people do on your website is going to decide whether it succeeds or fails, so think about what they need. Take two or three key processes you want users to take, and sketch out a rough "storyboard" of the stages they will take. For example if you're promoting a service, users might want to know they're in the right place, then see examples and testimonials to qualify what you do, and then get in touch.
It may be difficult to know exactly what features you need before you've spoken to web developers, but if you know you need a blog, or integration with Twitter, or a photo gallery, list these items. It may be useful to know the price of other features for the future, such as adding a customer login to an e-commerce site at a later stage. Don't emphasise features too much, because your web developer should be able to help you decide what features will achieve your goals.
Think about how much you're willing to spend and how soon you need your new website. This doesn't have to be definite but may help to rule out inappropriate suppliers, and give the others a better impression of what you need. Try writing a list of five or six factors that are important to you, and score each supplier out of 10. These could be cost (or value), agency size and reliability, technical knowledge, good communication, existing portfolio, or anything else that matters to you.
Trust your instinct
A brief should help you communicate what you need better and get in touch with the right suppliers, but the most important aspect of our relationship with clients is good communication. Don't underestimate the value of a good relationship, and treat your brief as a way to get to know suppliers.
If you want to read more, our friends over at Visme have written this article about Writing an Effective Design Brief