Don't add s to: afterward, backward, forward, toward.
As a general rule change -re to -er when it is the last syllable, as in theater, caliber, timber.
Beware of effect and affect, and use them carefully.
A long way, not a long ways.
Distinguish between: depository and depositary; between insanitary and unsanitary; between immoral and unmoral; between councilor, consular and counselor; between council and counsel and consul; between capitol and capital; between clamant and claimant; between sear and seer and sere; between emigrant and immigrant; between faker and fakir; between breech and breach; between auger and augur; between hoard and horde; between lessen and lesson; between principle and principal; between prophecy and prophesy; between advice and advise; between maize and maze; between site and sight.
The people of Panama are Panamans, not Panamanians, just as we are Americans, not Americanians.
Two cities in the United States take final gh. They are Pittsburgh, Pa., and Newburgh, N. Y. Also write it Edinburgh.
Drop the unsounded final letters in such words as program, catalog, suffraget, dialog, cigaret, decalog. Similarly, write armor, favor, color, and Savior.
Some words have lost prefix or suffix, and if they are in good use in their curtailed form, they should be written without apostrophes, as, cello and varsity.