To get the most out of testing,
Simple Language
Use a language your client can understand and relate to, avoid jargon where possible and explain what is happening if the client seems unsure.
Give Explicit Instructions
It is amazing how things that are very clear in your head don’t make sense to the client at all. As we do those tests every day we assume the clients will automatically know what we expect them to do. Alas this is hardly ever the case, so remember to go back to basics and provide clear and sufficient instructions.
Provide Tactile Clues
Tap on the body part indicating the direction you want it to move
Demonstrate The Movement
Where possible perform the movement yourself. Bear in mind that there might arise confusion with left and right if you are standing in front of your client and ask them to mirror your movements.