As a teen, I did quite a bit of work to keep my family out of my room. I come from a very large family, and I'd managed to turn my room into the cleanest and quietest place in the house, which meant everyone else wanted to spend a lot of time there (defeating the purpose of my clean, quiet space.)
I arranged the furniture such that anyone entering the room would have to walk through a narrow space between a dresser and wall, then walk all the way around my bed through another narrow space, before they could get to the open part of my room. I furthermore made sure there were no good places to sit except for my computer chair (by raising the bed to an uncomfortable height, and leaving piles of school papers stacked on my other chair, which I could easily move if I wanted company but nobody else would've moved.)
The best part was, I didn't have to make my room messy, smelly, or uncomfortable for me. I just made it uncomfortable for other people to spend time in the room without my intentionally creating space for them.
"I'd managed to turn my room into the cleanest and quietest place in the house, which meant everyone else wanted to spend a lot of time there"
How true! My home office was also my workshop/server room. I got tired of the heat, noise and technorubble, so I gave away the desk, moved the servers to the (much cooler) basement, and stripped the whole room down to just a sofa and mostly empty bookshelf. Now it's in high demand, and I only use it when I'm home alone. But at the same time, I got rid of all our towers and switched everyone to wireless laptops, so it's not too hard to find a quiet corner anywhere else in the house to work.
I arranged the furniture such that anyone entering the room would have to walk through a narrow space between a dresser and wall, then walk all the way around my bed through another narrow space, before they could get to the open part of my room. I furthermore made sure there were no good places to sit except for my computer chair (by raising the bed to an uncomfortable height, and leaving piles of school papers stacked on my other chair, which I could easily move if I wanted company but nobody else would've moved.)
The best part was, I didn't have to make my room messy, smelly, or uncomfortable for me. I just made it uncomfortable for other people to spend time in the room without my intentionally creating space for them.