How do you best tackle designing/decorating an empty space?

I am lost on how to tackle a blank room.

Specifically a blank bedroom.

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Most inspirations have much larger living spaces, and I cannot fit a lot of what I desire into such a small bedroom. I have all the measurements, but I am having a difficult time visualizing and planning. Even when looking at furniture.

I am curious. How did you all first approach designing your empty living space?

Did you find it easier to plan everything beforehand? Or did you find it better to tackle it in sections, keeping a small vision as you brought in key items, going with what most felt right?

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No matter how small of advice, I would greatly appreciate any input you might have.

Thank you.