Keep firing these type of questions
at yourself until it feels like you were there.
If anyone asks you a question
that you did not consider, you should still be able to
answer it convincingly very quickly as you have made
this scene so real to yourself that you know it backwards.
If there are other "extras'
in the background then bear in mind that although our
main characters are the focus for the reader there may
well be other events and conversations happening around
them. It shouldn't seem like the whole world has stopped
to watch your scene, life should be happening all around.
So make note of a few background events you can mention
in passing and maybe carry through some metaphorical
themes to mirror or juxtapose what your characters are
doing.
Are the characters using this
area for its intended purpose? (e.g. are they visiting
a hospital seeking treatment or are they breaking into
a hospital at night to steal drugs?) If they are not
using the area for its intended purpose then how does
the set up of the immediate surroundings conflict with
what they are trying to do?
Always draw out a map or diagram
so you can "walk' through the scene with your characters
and make sure everything happens logically.
Sometimes it's a simple style
choice: Let's imagine we're writing a scene where someone
is about to get shot.
Do we want it to be a shocking
surprise? If so the scene needs to be a happy and peaceful
one with bright colours and slow movement.
Or do we want the scene to be
filled with fear and foreboding from the start, building
to the shooting as the climax of a dark piece of writing?