If you are in the US or Europe, there is a list of exhibitions that you can’t miss. Of course, I suggest what I follow in the contemporary art world. This list underneath includes: New York, San Francisco, London, Paris, Oporto and Leon (Spain).
Guggenheim New York Maurizio Cattelan (till Jan 22)
MoMA New York Willem de Kooning retropesctive (till Jan 9)
SFMoMA San Francisco Richard Serra drawings (till Jan 16)
Tate Modern London Gerhard Richter retrospective (till Jan 8)
Centre Pompidou Paris Yayoi Kusama (till Jan 9)
Musac Leon, Spain is showing three great collective exhibitions (till Jan 8)
Serralves Porto, Portugal Thomas Struth till (till Jan 29)