Brand new to drinking, what to try and how to not sound dumb?

Hi all, I’m a 20 year old American who will be staying in London this summer for around a month and a half, so I hope to use the opportunity to drink a bit and check out local bars and whatnot. However, because I’m 20, I’ve never actually drank more than like, shots at a party. I’m wondering if there’s anything I should know to not sound or look like an idiot at a bar since I know nothing about alcohol and don’t know what I like or what to try. I’ve been trying to research different drinks to see what I should try but I’m curious if there are any essential or “must try” drinks for someone new to alcohol and drinking. Thanks!