Look for one-letter words. Because cryptograms often use quotes from people, the word “I” is almost as common as the word “a,” so be careful before plunging in. The trick to figuring out if it’s “I” or “a” is to experiment with the letters in other words. If there is a three-letter word beginning with that same letter, the letter is almost certainly the word “a” or “t.” There are a number of common three-letter words beginning with “a” and very few which start with “i.”
Try to identify the vowels. If you can find five letters with these properties, you have very likely identified the vowels (e, a, i, o, u) in that order. Vowels represent about 40% of the letters in English text. Vowels are present in almost every word. (Allow for rare exceptions like “my” or “NBC”.) Vowels rarely come three in a row, and almost never four in a row.
If you think an unidentified letter is a vowel, but you don’t know which one, use the following tips. The only vowels that can form a one-letter word are “a” and “i”. Unless the text is about skiing or vacuuming, a doubled vowel is probably “e” or “o”. The most common vowel is “e”; the least common is “u”.
The word “the” is extremely common and can be measured against “that.” For instance, if a sentence contains both “BGJB” and “BGD,” you can be pretty confident that you’re on the right track. In the same cryptogram, “BGDL” would most likely be “then” and “BGDZD” would be “there.”
Watch for apostrophes. One letter after an apostrophe is usually either “‘t”, “‘s”, or more rarely “‘m” or “‘d”. Two letters after an apostrophe is usually “‘re”, or “‘ve” if the letters are different or “‘ll” if it’s a double letter. Look at the letter before the apostrophe. If it’s always the same, you almost definitely have the “n’t” combination. If not, then you’re more likely dealing with the possessive.
Use clues from punctuation. Conjunctions like “but” or “and” often follow commas. A question mark often implies a “wh” in the clause preceding it.
Look for pairs of two-letter words, one beginning and the other ending with the same letter. That letter has a good chance of being “n,” “o,” “s,” “l,” or “t,” and the second letter of the word which starts with the shared letter is likely to be “f,” “n,” “o,” “r,” “s,” or “t.” If you find two two-letter words where the letters are reversed, you’ve got either “no” and “on.” You just have to figure out which is which!
A pattern of lots of repeating letters in a long word usually indicates vowels, like the “i” repeating in the word “civilization.” However, if adjacent letters repeat, they’re more likely to be “n,” “o,” “s,” “l,” “f,” or “t.”
Cryptoquotes end with the name of the author of the quote. Authors are usually identified as “first name last name”, but some exceptions can be exploited. “Anonymous” wrote a lot of great quotes. A two-letter word at the beginning of the author’s name is probably Dr. A two-letter word at the end of the author’s name is probably a suffix like “Jr” or “Sr” or a Roman numeral as in “Pope Paul VI” A short word in the middle of a name might be a common nobiliary particle like “de” or “von.”
Look for the following relatively common words that have identifiable patterns. That (or high, says, else, dead, died), There/Where/These (in any case you’ve identified “h” and “e”), People, Everywhere, Somewhere, William or Kennedy (if a name, otherwise maybe million or letters), Never (or state, fewer, color),
Learn the structure of English sentences. Recognize helping verbs to get hints as to what short words go where. Helping verbs are words such as Am, Be, Been, Have, Had, Could, Would, etc. Basically any word preceding a verb that describes what you are doing is a helping verb. They are never more than 5 letters.