Recently I've been having problems knowing when to double up the last letter in a short word when turning it into a longer word. When I was at school we were told that if a word had a short vowel sound like 'hop', you doubled the last letter to make "hopped" where as you didn't if it the word had a long vowel sound like 'hope'. It doesn't always seem to help though. For example, 'cancel' changes to 'canceled', but also to 'cancellation' - why? It surprises me how many words I misspell. The spelling mistake that annoys me most in other people is 'loose' when they mean 'lose'.