This may be quite a controversial question, but how many of you vet clients just as they are encouraged to vet you before purchasing a product or service?

My guess would be that most of you do, although no one would publicise the fact, after all we're taught to follow a rule that states we must treat all our customers the same - or must we? 

In business, and fortunately only rarely, you enter a conversation with a potential client and their air of arrogance conveys an opinion that you are one of the privileged souls they have given up their precious time to do business with.

You may ignore that gut instinct, honed from past experience, and forge ahead with a project, but it usually proves a big mistake when, despite having moved heaven and earth to ensure everything runs smoothly, Mr Nothappy or Mrs Nitpick suddenly call you up after completion to offer a plethora of unreasonable excuses for why they are unwilling to settle the balance. Among their absurd reasons for non-payment is the speck of dust you so foolishly left out of sight under the plinth. 

Yes - both Mr Nothappy and Mrs Nitpick are PCs - professional complainants - who have various tools at their disposal in order to continue their trade. Magnifying glasses, microscopes, test tubes, a Makita cordless for removing plinths, pelmets and cornices and a notepad that details those annoying, excessive and unfair grievances when you call round to try and rectify the issues.

They've now no means to continue their petty campaign but still manage to inform you that an upstairs radiator isn't working and the television has a less clear signal since the fitter finished the work. 

At this stage, you are left with two choices. Lose it with the customer and risk your reputation by the undoubted bad publicity they will bring to your door or cave in, placate them with a reduction in their balance and put the whole sorry episode behind you.

The option most likely, however, to have caused least worry and harm to your reputation is one they wouldn't expect and one you should have adopted when you first got a sniff of their game - ditch them. 

How you ditch them is up to you, but I suggest blowing a loud raspberry at them midway through, followed by wolf-like howls while doing your version of a rain dance around your central display. This will send them scuttling out the showroom to seek a more sane victim.

Customer service works two ways - the standard you offer them and the standard they offer you, and it's my opinion that both buyer and seller have the same rights in making that judgement. 

The customer may well be king, but we should never allow the customer to become a tyrant.