Hi FARM,
The simplest way is to read some of the basic information so you have a reference point to tell the people who know what they are talking about from those who don’t. Once you have this … then the goal is to connect with the “experts” who already know what you would otherwise need to learn.
One of the most important signs of a better retailer or manufacturer is that they understand the importance of providing you with the details of every layer of the mattresses they sell. These are the ones who want you to know the quality and value of the mattresses they sell. As long as you only consider mattresses where this information is available (in some stores it may be available for some mattresses and not others in which case I would ignore the ones where it isn’t) … you will be able to make meaningful quality and value comparisons between mattresses.
Some of the better options and possibilities I’m aware of in the Pittsburgh area are listed in post #2 here.
Phoenix