The aim of any complaint is to have it resolved. If a solution cannot be found, then both the person making the complaint and the business receiving the complaint lose out. Whenever someone makes a complaint, ask them how they would like to see it resolved.
Of course, the customer's ideas on how to resolve it won't necessarily agree with the business owner's, but whatever the outcome, it does need to be fair. I have had a number of complaints against business that have cost me a lot of money. In one instance I had to pay over $18,000.00 because of a company's negligence. They offered me $2,000.00 in compensation. This was, of course, ridiculous; what was worse, it was insulting. Finally they agreed to cover the mistakes and to pay the full amount, but by now the relationship was destroyed and there was no way we could ever do business together again. We both lost in this situation: even though I received full compensation, I lost good business relationship.
We all need to enter a complaint situation willing to resolve it. If the company you are complaining to is completely at fault, they will normally fix the situation quickly. There is no point in letting it drag on. If the fault is harder to determine, things can start to get messy. In some instances, it may be best to call in a professional mediator to try and resolve the complaint. This person is impartial: their job is to look objectively at the entire situation and find the fairest resolution to the problem.
Like all of the tips in this blog, the best solution is that the customer is satisfied with the outcome of the complaint and everyone moves on with their lives. Hopefully the customer will be impressed enough with your complaint resolution skills to keep using your business.