Graph paper is probably the easiest. Some patterns enlarge easy some are really a pain. You kinda have to know some math with some enlargements and REALLY know math with others.
If a block is made of 9 sub blocks, then it would be easier to increase it from 9-12in. a 5" block would be more difficult to increase to 9in. You can end up with some really odd fractions that aren't on quilter's rulers :lol:
There are also quilt progams that make it easier to do. EQ or the cheaper quilt wizard program both make it very easy to resize a block. I can draw a block pretty quickly in EQ and then size it to whatever I want and print out templates, not having to worry about odd measurements.