A lot of time in a consultancy can be taken up by producing estimates for clients so they can see a ballpark of what they will be spending. Because this time is not billed, it is easy to end up with rushed and inaccurate estimates, leading to problems later in the project.
A better way to go about it is to spend a little more time, and really get down in detail to what needs to be done. This is called a Specification review and is billable.
See Rules to Successful Sales Account Management.