I approach it at an ad-hoc basis and ask a bunch of questions to limit my options. What do I have in terms of furniture, what are the pathways to keep clear, how do I want people to move through the space, where is the light coming from, how many people are going to be here, where are the electrical outlets, and so on. So, a kind of feng shui without the mysticism.
Or are you talking about decoration? That I have a huge pile of framed art prints and they go up everywhere. If I was starting from scratch I'd probably keep it minimal and just use bright colours to break up large spaces.
I have classical art and design background. So, about 35 years of training in colour and composition.
But there's lots of rules of thumb out there about lighting and wall colours and where each should be what and why.