Hi chrischaos,
I think the first place I would start is
post #1 here
and the information it leads to. This is perhaps the most important post on the forum. This will give you the basic information that you need and the steps that can help you exclude some of the worst choices (such as Kingsdown or Tempurpedic) and focus on the better ones.
When you are starting out ... researching who to buy from can be even more important than deciding what to buy. When you find the "experts" that not only sell better quality and value mattresses but can also give you the help and guidance to make the best possible choices ... then you won't need to learn what they already know. They will "educate" you more than "sell" you. The information i linked to will help you recognize who they are.
Because of all the variables and personal preferences involved in choosing a mattress ... there is no "formula" that can turn height/weight and sleeping position information into an ideal mattress design out of the many thousands of possibilities that are available. While the mattresses section of the site has lots of information that can help you understand the ideas behind why different mattresses fit different people ... these are only generic and may not apply to any particular individual. They can help you work with the "experts" that are available to you more effectively.
The best way to know what is best for you is either through local testing (preferably with the help of someone with the knowledge and experience to educate and guide you) or if you are working with an online manufacturer then with a more detailed conversation where they can take your local testing on mattresses into account (if you know the specific layers and details of the mattresses you tested) along with their more detailed knowledge of the mattresses they make or sell and which of them may be the most suitable for you based on the "averages" of their customers that have similar body types and sleeping styles.
Once you have read some of the basic information ... then if you let me know your city or zip I'd be happy to let you know about some of the better options or possibilities I'm aware of in your area.
Phoenix