When he got to about 13 months, he was learning lots of new things, but couldn't tell us about it. So we gave it another go, this time he picked it up very quickely. He now uses signs for: hungry/eat, drink, hat, chicken, mandarine, more, where, done, washing hair, brushing teeth and nappy change. Together with pointing at things we have a very happy chappy who can tell us what he wants. Saves us both a lot of frustration!
He hasn't started talking yet, except for "pappa" and "mamma". But when he wants to start, he can say the word together with the sign, so we can help him with the pronunciation.