Since Playfair Puzzles are always encoded in pairs of letters, known as digraphs or bigrams, it is useful to know which are the most common in English.
The most common trigraphs are: THE, AND, THA, ENT, ION
The most common double letters are: SS, EE, TT, FF, LL, MM, OO
The most common letters to start a word are: T, O, A, W, B, C, D, S, F, R
The most common letters to end a word are: E, S, T, D, N, R, Y, F, L, O