Web Dev : How can I be a good client?

Paying on time based upon agreed requirements, mock-up, workflow plus milestones.

Create a mock-up on the design of what you want by putting in 3 references on the type of website design you prefer.

Creating the work flow on how your website is supposed to work from the start to finish.

Explaining it in what do you want to accomplish for your website in 2-3 sentences.

Don't constantly micro manage & change your requirements for the web design firm.

Instead ask for a weekly update with specific milestone to meet in face 2 face.

Be ready to negotiate on deliverables base upon your design, workflow, requirements and timeline.

Lastly prepare your finalised mock-up, website workflow and requirements before meeting the potential web design firm.

So you won't waste each other's time.