I've been reading this book on stuttering by Lee Loveet. He was a person who stutters and is now fluent. It's been a huge help. Here are some tips from the book for this exact situation. You can not say the word and use a different one. Drop the first letter of the word, most people won't even notice and it's not as bad as a block. Doesn't work for all words however. Whisper the word. Smile while saying it. Chang your voice modulation to higher or lower.