Some customers simply aren't worth the effort and then take time and energy from customers who deserve and will appreciate your attention, according to Michael Houlihan and Bonnie Harvey, authors of The Entrepreneurial Culture: 23 Ways to Engage and Empower Your People.

Based on their suggestions (and a bit of my own experience) here are the clients to drop from your roster:

1. Abusers

Regardless of how much they're buying from you, a client who yells at you and your team or uses demeaning language and expletives isn't worth keeping.

You'll never be able to please an abuser.  In fact, taking the abuse is implicitly asking for more. What's worse, if tolerate abuse for one client, you'll attracting others who do the same.

I personally give clients a free pass the first time they act like a jerk. (I figure everyone has a bad day.)  The moment I see a pattern though, it's hasta la vista, baby.

2. Agitators

These clients infiltrate your team and cause dissent, because they feel like it gives them an upper hand.

They spread false rumors, pass along malicious gossip and try to keep everyone scared so that they're easy to manipulate.

The moment you see a client attempting to "stir the pot," either isolate the customer to a single point of contact or tell the client to take his agitation elsewhere.

3. Ingrates

Even though you're delivering great work, these unhappy campers always find something to complain about, secretly hoping you'll do even more.

These customers are really morale busters.  While you shouldn't expect fulsome praise, trying to make an ingrate happy drains your energy.

I once spent a week preparing a 20-page project proposal only to have the client complain about a typo. So when he asked the price, I quoted my "go away" number ($100k). He went away.

4. Cheapskates

Cheapskates are always trying to bargain you down, even if you've put a lot of time and thought into pricing that works for your business and potential customers.

Cheapskates give a rolling donut about your hard work. They'll always ask for yet another discount or try to keep paying based on an outdated price list.

To make matters worse, they never pay invoices on time, causing you to have to spend time tracking them down in order to get paid. Spend your time and energy elsewhere.

5. Know-It-Alls 

These clients make you wonder why they even hired you. They don't take your advice, fight you at every turn, and then change all the work you send their way.

Even worse, when they do it their way and don't get the results they wanted, they find a reason to blame you or call you and need you to fix it under a ridiculous deadline.

Get rid of these customers quickly because you'll end doing way too much, lose money on the deal and even then they'll badmouth you to future clients.

6. Sponges 

Sponge clients seem to think they're your only clients and use your time accordingly. They call constantly, send email after email, and request needless meetings.

At the same time, they flake out on important meetings and deadlines because they view their own schedules as much more important than yours.

The time you spend hassling with a sponge is much better spent working with a customer who has a sense of perspective. 

7. Migraines

These are the clients who hold up a hoop and expect you to jump through it. Then they hold up another hoop, smaller and higher, and expect you to jump through it.  And so on.

They specialize in making unreasonable demands and last-minute requests that put unreasonable stress on you and your company.

The best thing you can do with clients like this is convince them to take their business to your biggest competitor.  Then you can sit back and laugh and laugh and laugh.

8. Threateners

These customers forever hold out the threat that if you don't comply with their wishes, they'll take their business elsewhere.

Whenever this happens, the best way to nip the behavior in the bud is to call their bluff by giving them contact information for your competitors.

They'll back down immediately.  And if they don't and actually call the competitors, hey, no big loss to you.

9. Liars 

These clients, you never know what's up or down. They'll say anything and everything to get what they want, regardless of whether it reflects reality.

They're always changing their expectations and deliverables and conveniently "forget" previously agreed-upon goals or deadlines.

You end up constantly second-guessing yourself or wondering when they're going to turn everything on its head. Don't waste your time. Go find some honest clients!