They will notice you. If you have any doubt about doing something, ask permission. It can save many hours of grief. The world is not as interested in your dislikes and hates as you are. Keep them to yourself, or between you and your friends, out of earshot of adults.
Nobody likes a complainer.
Do not make comments about other people's physical characteristics unless, of course, it's a compliment, which is always welcome. If you are unsure, get your parents to teach you. And watch what other people do. Add something pleasant to the conversation. Talk, don't just eat, and don't eat as fast as you can.