Poor Support
If you hate getting onto a website where there is no way to contact someone when you have a problem, or if you hate being on hold waiting for help, or if you feel frustrated when the company support personnel completely fail to answer your needs, do you really think that your own customers are going to be satisfied with a halfway effort from you?
Not all businesses require support services. Most do though. If you sell anything, you need to provide a means for your customers to contact you with problems. If you write instructional materials, you need to provide a way for people to give you feedback. If you offer services, you need to have a clear and effective manner of addressing issues of satisfaction.
And your support should be generous. So you built a computer and the person is calling you with a software issue which really ISN'T your fault, nor is it covered in your warranty. You can at least be polite, help if it is quick to do so, or point them in the right direction to get the help they need. Yes, time is money, and politeness and helpfulness can cost you a bit of time, but it can also give you a loyal customer for life, or your refusal to give it can cost you a customer, which will be worth a whole lot more than the few cents that courtesy would have cost you.
The worst thing with support is none at all. I have had problems with items I purchased, and have not even been able to get a reply to my problems. One fairly prominent company that I purchased a service from refused to help me over the phone, and required that I email them. I did so, three times, and they did not even answer my emails. I not only no longer have an account with them, but I stopped promoting them through my affiliate link as well. Prior to that, I had brought them many new accounts, but no longer recommend them - in fact, I warn my clients to avoid them.
Support information needs to be clearly displayed on your website, and assistance needs to be given promptly and courteously. When someone is having a problem with something you sold them, they won't be happy with you again until the problem is solved. The longer they feel badly about you, the less likely they are to purchase again or to refer others to you. Delays and rudeness are not good business!

