A good system to follow is to consider "pencil" pressure - the pressure you exert pressing the point of a pencil against a piece of paper as you write. Put a piece of paper on the platform of a postal scale, for instance. Then, resting the weight of the hand on some surface (like 3 book) that is about level with the postal scale platform, write with a pencil in normal fashion on the paper on the postal scale platform and read what the scale dial tells you in.