You've heard the expression "time is money" well as a freelancer that is the absolute truth. Working with your client efficiently will free you up for more projects or more leisure time... (win-win).
So how do you work more efficiently? By thinking ahead.
For example, I'm working on a major web site now and my processes is to get an approval on the home page before I show an interior page.
Now my client was expecting one interior page, but I noticed that there were actually 3 different major interior pages (one for one type of chart (30 pages), one for another type of chart (30 pages) and one for basic information (10 pages) so I presented all 3 in 2 different versions.
All my client had to do was pick which background they liked best and which navigation structure they liked best.
Sure, I spent more time doing the work, but in the long run it was more efficient to do so and it made my client feel better seeing the differences before I went into the entire site.
Bottom line... sometimes it pays to spend more time to make the project go faster... then it becomes more profitable!