There are some letters that are always doubled at the end of a word. This quick movie gives an idea of how to remember which ones.
This link takes you to a downloadable poster of the poem in the movie.
http://www.gdss.glasgow.sch.uk/Websites/SchSenRosepark/UserFiles/file/Spelling/flossy%20poster%202.pdf
EAL Service and Glasgow Dyslexia Support44 Carmichael PlaceGlasgowG42 9SYPhone: 0141 483 2960