BackPacker,
Likewise - I didn't think of this method of 'remembering' formulae until a fantastic day in a Chemistry lesson when it struck me. Been using it ever since and it's brilliant.
Regarding only using SI units - that's not quite correct, you just have to be using the
same units throughout, e.g.
P = pressure in PSI (pounds per square inch)
M = mass in pounds
A = area in square inches
then P = M / A
which
reads as pressure equals mass per area, and 'per' just means divide
