It is bad taste to yawn in front of people. When one unexpectedly has to yawn, if he rubs his forehead in an upward direction, the sensation will stop. If that does not work, he can lick his lips while keeping his mouth closed, or simply hide it with his hand or his sleeve in such a way that no one will know what he is doing. It is the same with sneezing. One will appear foolish. There are other things besides these about which a person should use care and training.