What is the best way to prepare for the USCIS writing (dictation) test?

The best preparation for the writing test is to practice writing sentences made from the published USCIS writing vocabulary: people (Washington, Lincoln), civics terms (President, Congress, White House, vote), places (United States, Washington D.C.), months, holidays, and common verbs and connecting words. Because the dictated sentences are built only from this list, repeated practice writing such sentences — especially the commonly misspelled words like February, Independence, and Congress — prepares the applicant for whatever sentence the officer dictates. Memorizing a single sentence will not help, since the officer chooses from many possible sentences using the vocabulary list.