Rooming with sister tips?

I've never shared a room in my life, but now I'm getting two little sisters to share my room with. They are 7 and 8, and I'm 12. (They're my dad's girlfriend's kids and she's moving in with us) There are no bunk beds (we tried looking for one), so there are three single beds. It's kind of a big room, but I'm sure with all the furniture it will be small. So, any tips or things I can do to make it either roomier, more room/space, or anything else. (: Thanks!