Advice on room modelling for game engine

Hi All,
I’m getting to grips with Blender and want to model a several rooms linked by a corridor, for use in the game engine. I want the room to have windows and will obviously will be doing a skybox.
So far I’ve tried using flattened cubes as walls and then using booleans to remove the window geometry, which resulted in simple geometry but triangles and thus dodgy shaped textures (as I applied a wallpaper to the walls). Then I built the walls using extruded planes, however the textures were complex and the walls had missing edges and faces for some reason.
I’ve done a lot of searching around and there aren’t any tutorials on how to go about doing a room efficently for the game engine. There are tutorials on all the separate elements but it’s very tricky for a newbiw like me to pull them all together.
Could anyone give me advice as to how to go about modelling a low poly, simple geometry room that will be easy(ish) to map textures onto and that will do okay in the game engine?
Thanks for any help, much appreciated.