I published a pattern last year, a quilt similar to my avatar, and I don't really expect to publish another. I only did that one because I had so many requests from board members. I have had far more pattern sales than I expected, almost all through this board. I am selling a few on ebay as well.
Jaciqltznok has brought up a lot of valid points. When I decided to make my pattern, I bought Publish Your Patterns by Nancy Restuccia. I highly recommend that book. When it came time to calculate yardage (I had an advanced Excel spreadsheet set up) I came up with an algorithm and listed it in the pattern:
"The fabric requirements on the back of the cover page are computed to allow for some squaring up and shrinkage. In general they are calculated by computing the length of fabric needed across the WOF (assuming 40 usable inches in WOF), adding 3", and rounding up to the nearest quarter yard. They do not allow for making experimental blocks, excessive shrinkage, or misadventure while cutting or sewing. It is always a good idea to buy a little extra if you can."
When it came to testing, I asked 6 members of the board to test, thinking that maybe 3 would agree, and was astonished when all 6 agreed to test. Not all finished the quilt, but all of them did give me good input. In fact, most of the testers had trouble with one aspect of the quilt. This led me to completely re-think the techniques, re-write the pattern, and invent the paper template to be included with the pattern.
My main advice would be to consider the numbers and your purpose. If you sell your pattern to quilt stores, they will give you only 50% of the retail price, and you still have to pay for the printing and packaging of the pattern. Wholesalers take a bigger percentage, so you may be paying all the expenses of pattern production from as little as 25% of the sales price. If you're doing this for the income, you may be disappointed. (I would say that you probably will be disappointed, except that the quilt you showed us is so spectacular.) If you're doing it to share your patterns with others, you will be blessed by the positive comments and friendships that develop. Good luck!
As far as Judy Niemeyer's patterns go, they are beautiful. I own 7, have made 1, am in the process of making another, but I have found a number of significant errors already in the pattern I'm making, and they are not addressed in the online corrections. I have sent an email to her, but haven't heard back yet. One of the errors was that she said to cut 40 strips, where only 20 were needed. I would have been pretty upset if I had not caught that one before cutting. I always check over the math in the patterns before cutting.