Whether you're an entrepreneur or an account manager for an established firm, you're always happy to have new clients. Clients supply your revenue -the lifeblood of your business--and as long as you keep them happy, the relationship can be both beneficial and pleasant for both parties. Most clients, if treated with patience and respect, will return it in kind, establishing a mutually beneficial and rewarding professional relationship. But unfortunately, some clients fall outside these parameters.

No matter how much you vet your clients or strive to preserve healthy client relationships, you're eventually going to get a nightmare client who presses your buttons and pushes your patience to the brink.

Keep watch for these seven types of nightmare clients:

1. The Bureaucracy. The bureaucracy isn't necessarily a person--it's an entire organization. There may be a dedicated representative that you communicate with, but behind that face is a gigantic, complex organization filled with rules, procedures, and committees. That means every decision that you need to get will probably go up the ladder, get squabbled over for several days, and then come back down in the form of a non-answer, like "we like it, but don't really like it." This client is particularly difficult because you'll never work with any one decision maker, and making progress on anything is going to take a painstaking amount of time.

To better manage this client, try establishing a designated representative who will make all final decisions on behalf of the bureaucracy.

2. The Mind Changer. The mind changer is notorious for changing his opinion at the last second. Let's say you've established a product order for 500 units, shipping out on Tuesday. You get an email Monday night along the lines of "did I say 500? I meant 1,000," which wouldn't be so bad if it didn't seem to happen with every single exchange. Worst of all, these changes often come by last minute, forcing you to change course and costing you precious time.

To better manage this client, establish firm "signoff" procedures, which cement work agreements in writing and allow for penalties or alternative circumstances when the outlined work is changed.

3. The Needy One. The needy client is following up with you constantly, from the time you begin working together to the time the project is done (and sometimes thereafter). She demands an update every day, even if no progress has been made, and causes your phone to ring off the hook. She wants to do a good job for her company and make sure the job is going well, so it's tough to be mad at her, but her constant following-up and requests for more information are interfering with your ability to actually get the job done.

To better manage this client, establish set weekly meetings and adhere to them. If she reaches out before the meeting, take note of her questions and address them only during that scheduled meeting.

4. The Micromanager. The micromanager is sure he's better at your job than you are, and he's questioning every strategy you make. If you're under contract for SEO services, he's overanalyzing each of your articles and all of your strategic link building choices. If you're designing his website, he's questioning the color of every link and button, and is offering suggestions of his own. Critical eyes for detail are important, but nitpicking every single choice is counterproductive.

To better manage this client, start high-level; seek approval on concepts and outlines before digging deeper into the details. You'll save yourself a lot of headaches.

5. The "Everything's Urgent" One. This client has no sense of distinction between a minor issue and a genuine cause for alarm. You can tell because she marks all of her emails as high priority and often calls you in a frantic state. Every small issue is magnified to infinite heights, and every hiccup in the process is grounds to abandon the project altogether.

To better manage this client, work on a mutually agreeable category system; for example, in the web development world, you might sort web issues into "A-level," "B-level," and "C-level" priorities.

6. The Dictator. The dictator refuses to listen to anything constructive you have to say. He's already got his mind made up, and he'd rather disregard your expertise than deign to compromise his initial vision. Anything you try to suggest becomes an argument, and he's not willing to listen to reason. Overall, you end up losing productivity or quality on almost every job.

To better manage this client, set firm yet reasonable expectations at the beginning of the relationship. Establish yourself as the authority, and listen to his advice, but stand firm if what he says goes against your better judgment.

7. The Incomprehensible One. The incomprehensible one is almost impossible to understand, either because she doesn't speak coherently or because she's so disorganized you can't wrap your brain around what she's asking. Either way, you'll have a hard time discerning her intentions and keeping her happy as a client. The communication barrier is often so strong you won't be able to come up with a good plan forward.

To better manage this client, be sure to recap everything in writing, whether it's a conference call meeting or a brief email exchange. Get her to verify that your understanding of her is correct before moving forward with anything significant.

Dealing with nightmare clients is a headache, but it's an unavoidable one. They'll likely pop up no matter how hard you try to avoid them or weed out the problem partners when you notice the issues. All you can do is remain patient, understand the different archetypes, and refine your approach to keep the relationship moving as smoothly as possible.