The Ultimate Guide to Testing Soil pH
Hanna Instruments has an all-encompassing guide to help anyone who is just starting out with soil pH testing. (And experienced growers will be able to learn something, too!) In the first part, they cover everything from "What is pH?" to elements and events that affect your soil's pH, and how to fix it. After that they go over all the different soil testing methods and tools, so you will have all the information you need to choose the best soil testing plan for you and your crops.
Check out the guide here.