For dowsing or muscle-testing, though I’m not familiar with the author (link below).
I use a pendulum myself and it took me about 6 months initially to feel comfortable in just testing supplements [which answers would get confirmed by my chiropractor or someone else trained well in muscle-testing]. Muscle-testing btw, helped find a cause of higher blood pressure I had years ago, and the answer was in taking a probiotic. Within a week, I was feeling much better and continued to take it for awhile after, as for some reason, coffee seemed to be a culprit in wiping out good bacteria.
http://www.healing-with-eft.com/muscle-testing.html
Some of her self-methods in a related link I’m unfamiliar with; I’ve heard of the ring finger; also where you hold onto a particular supplement and feel a tendency to move forward
(meaning a yes for you) or backward
(meaning a no). It’s important to remember that no doesn’t always mean negative, but that it’s a no for you (the one who is doing the testing) at the moment. Important also - be well hydrated.
This type of testing can be used to ask other types of questions in your life (it’s important to be very specific though, clear of mind, be appropriate [ask God], and make them as statements so you can get a yes or no) – what I always found wise until I got more comfortable with it, was to make a question list, and have a practitioner to muscle-test those questions randomly so I didn’t know what they had in mind when they tested; it’s a good confirmation that way. If ever my pendulum goes "wonky", I will take a moment to relax and then test again. Sometimes, leaving it [as a methodology] for awhile is best too and just trust Life.
Practice, practice