As opposed to high anion gap acidosis (which involves increased organic acid production), normal anion gap acidosis involves either increased production of chloride (hyperchloremic acidosis) or increased excretion of bicarbonate.
One more commonly used older mnemonic is "USED CARP":
U - ureterosigmoidostomy
S - saline administration (in the face of renal dysfunction)
E - endocrine (Addisons, spironolactone, triamterene, amiloride, primary hyperparathyroidism)