A CTO blogger made some observations about consulting and how to maintain a respectable level of professionalism. The 5 areas of focus he discussed are described below with my own perspective thrown in to the mix.
Be Customer Focused
The customer's project is not your playground. It is not a place where you do things just to see if they'll work. Instead, you need to bring your experience to the table and apply it to the environment that the customer is in and obstacles that the customer is facing.
Keep Up to Date
You are the expert. Make sure you stay the expert. That means reading and learning all of the time. This is especially true in the information technology field where everything changes very quickly.
Make Every Hour Count
Although it should be a goal to charge as much per hour as possible, you need to make sure that every hour provides value. If you misstep and need to redo some work, consider not billing the client. The line between what is your fault and what is the client's fault isn't always clear so you'll often need to do what "feels" right.
Guide the Customer
As a consultants you need to offer solutions to resolve problems. Your opinion won't always be followed at first. It therefore becomes your responsibility to gather all the pertinent information and help your client to the right solution.
Look for Opportunities
Regardless of how specific your task is, keep your ears and eyes open for other opportunities to help. It is quite possible that while working on your task you will come across some other process that could be improved. When you do, don't keep the information to yourself. Instead, share it and propose how you could be of assistance.