We have a fairly small house so I avoid green fluffy type garlands. On my mantle (which is basically a 1m length of wooden beam) I have a wooden garland with berries on it intertwined with a set of red berry lights across and a red lantern with a battery candle in on each end.
I have a bookcase that usually holds photo frames - I remove these and replace with some ornaments.
We have a tree that probably shouldn’t work but I love it. It has coloured lights and no colour scheme. It has more decorations than it probably needs but that adds to the charm.
Same as pp, I also swap the usual blanket for a Christmas one.
We have a conservatory and in there we have some awful lights on the windowsills (LO loves them) and I put our advent calendars out there on the dresser. It also has a skinny tree that we don’t decorate out there which is pre-lit with warm white lights.
I don’t really decorate anywhere else except the hallway. We have a small set of draws that is a shoe holder and I swap the plant on there for a porcelain Christmas tree.
What I would say is less is more which is why we swap rather than add things, and cosy is nicer to sit in than opulence.
What you do is going to depend on the type of house you have and how you use it (for example at my mums she can’t decorate her hallway, it’s too small and busy but she has a sideboard in her kitchen that she goes OTT with).
Have a look on Pinterest and steal/adapt the ideas you like - then come back and tell us what you did 