If I am honest Dean, I think you are approaching the problem from entirely the wrong perspective. Who says that the client cannot contribute design ideas?
Anybody can make good design suggestions
Did you watch the matrix films? Were you disappointed in the way the trilogy concluded? The rather pathetic ending was made all the worse by the fact that the web was full of great ideas about who the series could have ended. The endings suggested by fans were often far better than the one chosen by the professional film maker.
The moral of this little story is that anybody can have a good idea. You don’t have to be a professional film maker to come up with great movie concepts and you don’t need to be a professional web designer to improve a site.
Clients can and often do come up with great design ideas. We need to accept that, and not reject them just because we didn’t think of them.
Our experience and expertise will probably give us a higher hit rate than a client, but that doesn’t preclude the clients contribution.
The challenge comes when they have a bad idea.
Dealing with bad ideas
Although I strongly believe the web design process should be a collaborative one between client and designer where both are equal partners, that does not mean both have the same expertise.
As a web designer we spend a lot of time learning from the client. They tell us about business objectives, target audience, branding and much more. It is our job to soak all this up and theirs to explain things as clearly as possible.
This is a two way street. It is also our job to teach the client. To explain clearly why an idea they have will not work and to do so in a non-confrontational and gracious manor.
A good place to start is by asking why. Why does the client think their idea is a good one? Why would the site be better in green or what does making the logo bigger achieve?
Questions like this help get at the underlying issue. Most client ideas are their solution to a perceived problem. If you understand the problem then you can comment objectively on the solution.
For example, if they want to make the logo bigger this maybe because they are concerned the branding is being lost. In such a case you might decide the client is right or that increasing the amount of whitespace around the logo achieves the same thing.
If you and the client disagree about the solution to a particular problem, don’t allow positions to become entrenched.
Start by appreciating their contribution and try to encourage them about some aspect of their solution. Show you see them as a valued contributor and not as a nuisance.
Instead of directly criticising ideas, ask a few questions. For example, instead of saying “you can’t make the logo bigger without distracting from calls to action”, say “have you considered how this might impact our calls to action? Are you okay if they become less prominent?”
This gentler approach is significantly better than stomping your foot and demanding to be listened to because you are the web designer. This just comes across as desperate, aggressive and undermines your credibility.
This is a massive topic and there are no shortage of approaches you can use (hence I wrote an entire book on the subject). It would be interesting to hear what other approaches work for people in the comments.