So basically, today, I figured out I could potentially get into every common room, no matter what House I’m in. (I’m a Slytherclaw)
Slytherin - Legit, just say something offensive. There’s a good chance that’s the password this year. If you’re wrong, keep trying, you’ll hit on something revolting sooner or later.
Ravenclaw - Riddles? I am all about riddles. Also, I’m clever.
Gryffindor - Make friends with a Gryffindor. Complain that your common room isn’t as cool as theirs. Inflate their ego. Ask if you can hang out there instead. Or be Neville’s friend. Rowling knows that kid could use a friend.
Hufflepuff - The only house that is not obvious to get into. We know where it is, we know it’s hidden behind barrels, but the exact details of how to get in are a mystery. I bet you just have to be nice. Like “Wow, barrels, your wood is looking really smooth and shiny today!” Yeah, that sounds like it would work.