Simply attempt to get as close as possible to the usual driving posture, like you were in a real-life racing car. Livingroom divans, different tables, armchairs and secretaries will not do the job like a real car driving simulator chair will.
The authentic driving environment is nowhere close to the aforementioned household chesterfields, armchairs, secretaries and benches, isn't it? So, at least you should try to have the proper racing position. If you do not, you will not be able to perceive the actual potential and joyfulness the current car driving home video games are supplying. It's as plain as that.