Not embarrassing your child

Try not to embarrass your child in public.
For example, if he wants to take his dummy or teddy-bear with him , don't say "You're too old to play with teddy-bears" or "Don't be a baby", leave your dummy at home".
What's best is to take him/her aside and tell him ask him why he needs to take his comfort toys with him.
By doing so, he'll realise himself that he doesn't actually need them and that he's old enough to go without.