Every now and then you receive a client who gets involved in your end of the deal, and is questioning / making firm suggestions about directions to take. This could be due to their eagerness, misunderstanding of professional boundaries or personality; but it needs to be addressed when they begin to intrude too much upon the design of your project; to its detriment..

I have found, the best way to approach this niggle in la backside and take control is to explain why you are the designer and they are the client.
Experience
Make sure you take the time to explain that you are the designer and as such have a wealth of experiencing designing and they well… don’t. This is often a hard point to word without being antagonistic but make sure it is seen as a simple statement and not a call to argument.
Professional Skill
This is the point that you should be itching to use in your arsenal. You have reasons behind your madness – explain them. Explain why comic sans and neon green is not the correct brand colour for an emerging accountancy firm. Explain why that subtle flick on the tail of a character of text is a key element to the design. Explain why flash should be used sparingly when it is not appropriate etc
Homework
Another great approach is to validate your concerns as to why for instance a huge flash splash page is not necessary, is by letting the client read up o the issue. We have a great design community full of loads of little articles explaining many issues you may come to loggerheads over. Take the time to source something relevant and send it over to them.
It is also important to approach the situation from a professional standing, and ask why you object to their suggestions?
Pride
With every project, it is essential to maintain a professional distance. This distance is what allows you to evaluate their suggestions and to be objective. You need to ask, are you opposed to their intrusion because they are going to break the site’s function or logo’s fitness for purpose? Or are you opposed because you really think doing a certain something in a certain way will look great in your portfolio?
Contracts
This situation amongst others is another wonderful example of why having a detailed and pragmatic contract is essential! Ensuring that design revisions, what constitutes a revision, extra fees for extra revisions & how many revisions are included cemented within the contract protects both of you. Controversial to say, but if your client is adamant and set upon their course – remember two of the key points here are to provide what the client wants and that you are a business and such are being paid. If the client wants to delay proceedings by a month to see how a new web design will look, or to receive 4 more logo concepts, GREAT… show me the money.
Outside Perspective
There is no harm in seeking outside perspective… ask a fellow professional and if applicable ask a somebody who is not a design professional. Maybe your judgement is off and maybe this may be one of the rare situations where you will have to hold your hands up and say… ‘I was wrong’