Like a lot of the others have mentioned, I like to have a variety of sizes. I like the fabric requirements on the back. I like to see the block size on the back, the number of blocks, and the finished size(s) of the quilt.
If I know the block size, the number of blocks and the finished size for one size, I can usually figure out pretty easily in my head how many blocks I'd need if I want to make a different size. From that, it's fairly easy to estimate the fabric requirements based on the fabric requirements for the size that is given -- and buy a little extra to make sure I have enough :) I do realize that I am pretty good at math and those calculations would be difficult for a lot of people, so it's best if the pattern has multiple sizes.
And be generous with the fabric measurements. If possible, allow for cutting a strip wrong and having to recut. Some fabric shrinks a bit if you pre-wash. Other fabric that looks like it was cut straight loses it's straight edge when it's washed because it was pulled off grain when it was put on the bolt. It's very frustrating to get almost done cutting and realize that you don't have enough fabric.
Julia in MN