sometimes trades do have semi-secret techniques evolved from dealing with the same damned issues over and over and over again.
This is the thing that keeps me from building my own tables, chairs, whatever. I know with many categories of things, even if building my own is 20% cheaper, I will still require 3 revisions to get it right.
We are so used to tailoring one-off solutions in software that we can't imagine just taking some boring old woodworking plan and using it as is to quickly gain experience and produce a solid first result without R&D headaches. But in woodworking you really can just take someone else's design and build it. Most likely the designer already made all the mistakes before, so the thing will just work. You'll learn the techniques, and by asking why often enough you will trace back to the problems solved by various design elements. You will have a better idea of what to innovate yourself next time. Besides all the learning, you'll have a functional thing that you can keep, sell, or give away. (Says the guy who had to design his own banjo, still isn't done, and could have built two or three in the same time by copying instead of analyzing every feature from the ground up.)
Try Popular Woodworking. They have some of the most accessible projects. For a really interesting/exciting small publishing company take a look at Lost Art Press. LAP is sort of the Pragmatic Programmers of the joinery world.
If you're feeling adventurous, carry a tape measure and check out the size and shape of furniture around you.
If you really start getting in to designing furniture "The Measure of Man and Woman" (http://www.amazon.com/Measure-Man-Woman-Factors-Design/dp/04...) is full of useful measurements and ranges that tables and chairs should satisfy for average, 1 percentile, and 99 percentile humans.
Wood is actually pretty forgiving. You can prototype the size of something in cheap pine, and remember, it's always easier to cut off another inch from those table legs then it is to add one!
It also depends on your tolerance for not 100% correct. I've got a ton of stuff i put together that's functionally perfect but doesnt look like it belongs in a showroom anywhere (unless its abstract art!)
This is the thing that keeps me from building my own tables, chairs, whatever. I know with many categories of things, even if building my own is 20% cheaper, I will still require 3 revisions to get it right.