Spark Plug Torque

I tighten mine until my elbow clicks

I normally install the spark plug til it's fully seated and hand tightened, back it out and re-seat it and hand tightened again, then turn the plug socket an extra 1/6 of a turn (this will ensure the crush washer is bedded in). There is a recommendation of 20-30 Nm of torque, but I have never used a torque wrench for plugs and also have never had an issue with plugs being loose or over tightened using the 1/6 turn method. Here's a guide on the Denso site for various plug designs if you aren't confident in going by feel - SPARK PLUG Installation | Basic Knowledge | SPARK PLUG | Automotive Service Parts and Accessories | DENSO Global Website