Telephone and LAN/WAN systems have become increasingly complex and more interdependent. Properly implemented, top-quality systems can significantly enhance both productivity and customer service.  The challenge for business owners and managers is to understand how to make good purchase decisions in this arena.  The foundation of this understanding is to articulate the criteria on which those decisions will be made.

So, what decision criteria should you use? 
The "Business Phone Systems Guide" is a periodical published by Better Buys for Business, an independent consumer guide to office equipment – typically available in local libraries.  The section titled "Our Most Important Piece of Advice" applies equally to voice and data systems: 

"If we could provide you with only one piece of advice in this article, it would be this: it is vital that you deal with first-class people when you get a new system.  It is better to buy an average system from a superb group of people than to buy the finest system from a bunch of idiots or from people who lack experience or just don't care. A poor installation will sabotage the best phone system.  Bad or thoughtless wiring will leave you with a headache that will bug you for years. Careless programming will mean that you'll never get the most our of all those fancy features.  And inadequate training will mean that no one will have a clue how to use them anyway." 

Assuming one accepts this advice, the challenge is to be able to review and assess the qualifications of potential vendors and assign some values to aid in comparing the vendors (and the equipment if multiple manufacturers are under consideration).

If you considering solutions from multiple vendors, one approach is to construct a "Value Equation".  Here are some of the reasons that decision-makers have given for using that approach: 

"It forces us to establish and articulate what we need to accomplish."
"It reduces potential for an emotional, non-empirical decision."
"It helps us and our business partners stay focused on what is most important."
"It's the easiest way for us to explain our decision to our board and the other vendors."
"It provides the best way to give all of the people on our evaluation team equal input."
"It provides a logical conclusion to the technical requirements."
"It ensures that we get the information we want from each vendor."