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Measure your full space; top to bottom and wall to wall, being sure to account for how much space you will need to comfortably move around once the furniture is in place.
Consider how much you move around while working. Do you tend to shift around in your chair, lean on your desk, or rest your feet on parts of your furniture while you work? If so, you will want to invest in a chair or desk with stronger joints that will not make audible pops and creaks as you move around.
Confidence is the key to a good performance. Your voice can't convey confidence if you are worried you're going to knock something over or are sitting in a chair that feels unstable.
Remember that different materials behave differently in changing conditions. Wooden furniture is not a good idea in areas with changing humidity. Metal tables are prone to pop and click when temperatures change. Plastic is much more sensitive to changing stress and pressure which could also generate unwanted adjustment noise.