Finding a room in a shared house is a bit of a gamble. Going into a home where people are already settled, or moving in with people new to the home can be a daunting thing.
You can’t control how people are, but you can look out for certain things that will help you to discern if this is a property you would like to live in.
Cleanliness is a big factor. Is the home well-kept and tidy, or is there random junk and personal belongings strewn across the place?
The kitchen area usually gets the most use in many shared houses, how is it? Remember you are going to be preparing your meals there every day, is it an area you would like to use?
How is the room you will be sleeping in? Move around in it and feel for any drafts. Take note of the other rooms that share the same walls, could they be potentially noisy or cold? If so this will also transfer into your room too due to the proximity.