1| If you're not sure if your prints match, try matching your colors. Monochromatic prints will definitely work, and luckily, most fabric lines produce several patterns in the same color, so the work is already done for you.
2| Find a print you like, and then pull one or two of the colors to find a coordinating print. For example, try starting with a floral print, then add a geometric print in one of the colors from the floral print (i.e. stripes and florals or dots).
3| Think about the scale of the print. Usually, a small scale print pairs best with a larger scale print, and large, contrasting prints (and colors) work well, too. Lots of small scale prints can be too busy and can overwhelm the eye.
4| When all else fails, don't think at all, just mix as you please!
|image from The Hunted Interior|
|image from Interiors by Lisa Kahn|
|image from Project Nursery|