Using 'and I' inappropriately
People are constantly saying 'X and I' when it should be 'me and X'. Occasionally it's the other way around but rarely, I think people just think 'X and I' sounds more fancy. All you have to do is say it as you would without the other person and then add them in. For example:
I went to the shop = X and I went to the shop
Do you want to come to the shop with me? = Do you want to come to the shop with me and X
SO many people don't understand how it works and it drives me insane. Script writers on TV, YouTubers, people in significant positions (MPs, lecturers, teachers). The Queen used 'my husband and I' in speeches when it was grammatically appropriate, not just because she was posh!