There are no rules for theremin technique the way there are for violin or cello. There are many books and videos on the subject but there is no "one size fits all". The best method for one player is not necessarily the best for another.
My advice (and I have been offering it for years) has always been for newcomers to the theremin to listen to as many thereminists as they can and imitate, as closely as possible, the method of the player they like best until their own style automatically kicks in. This can take anywhere from a few weeks to a few years.
Never take advice on theremins or theremin technique from anyone you have not heard play, or from anyone whose playing you do not enjoy (that includes me). 
"First, have music in your soul. If you have THAT you will find a way to do it." Clara Rockmore
"Everything has already been said but since nobody listens you can always say it again." André Gide 