We keep having meetings about the design, the layout hasn't changed it's just nitpicking about colors and textures etc. and nobody has any actually constructive criticism. Nothings really changing, just shifting things around CONSTANTLY, how do you tell your client to shut up and let you do your job?
You have to steer the process and guide your client from start to finish.
You need to be selective about the type of feedback you are looking for. Don't ask "What do yo think?" but rather, ask specific questions that aren't subjective in nature.
Justify your decisions. Give explanations as to why you chose certain design solutions over others. That helps them understand that there's an actual educated thought process behind it rather than you randomly picking colors.
Have them define their market, their users, their business sector. Doing this helps them see how their design solution fits into the overall market space.
Be firm on budget issues. If the client is just belligerent and has randomly changed colors for a 4th time, say "we can certainly do that. However, we're now out of scope from the original contract. I'll get a revised proposal to you with these additional costs included for your consideration." A lot of the time, clients will continue to nit-pick if the meter isn't running.
Make sure your projects have defined timelines and both you and the client have a firm calendar of due-dates for deliverables and sign offs.
Route communications with your client through a primary stakeholder. You want them to come to consensus before meeting with you each time rather than you having to take the responsibility of building consensus through the group.
When clients offer an opinion, ask them to frame the opinion in terms of business needs and requirements. If they say they want something pink, make sure they have a reason by asking "we can certainly use pink. However, my understanding of the market was that industrial power washing equipment is primarily a male dominated market place. Have I misunderstood our target audience?"