My experyise in the art of making a small room look bigger extends to:

a) painting the walls a light blue or light blue-grey, to imply
distance,
and
b) introducing some horizontal lines into the paintwork and curtains.

Does anyone know of any other tricks one can employ?

The room in question is only 3m x 4m, and I have to make it look as
spacious as possible....

Thanks

Frank