Acceptable play in Ailerons, Rudder and Elevator
I have found it useful to make a gauge for checking control surface play (see picture). So when it comes time to check that, rather than having to look up the values (which I can never remember year to year :-) and marking a ruler, I just grab the gauge and work my way around the airplane. I suspect I'm not the first one to do this.
References: The elevator value came from Ercoupe Service Memorandum 56. The rudder value is used for compliance with recurring AD 57-02-01 and the aileron measurement is specified in Ercoupe Service Memorandum 57 for aircraft which have had the aileron balance weights removed.