Anyone who types on a regular basis will understand how easy it is to make a typing error. This happens frequently with proofing. In fact with printing, one thing occurs almost as much as typing errors, and that’s customers not finding them. This is the reason why we insist you see a proof before we proceed with printing. Believe it or not, I once had a client who missed the incorrect spelling of their name on a business card and I’ve lost track of how many people have missed an incorrect phone number. The best advice I can give is to take your time and read everything thoroughly. We have a blog post dedicated to this subject. Asking a friend to read the proof will also minimise the chance of errors slipping through.