This definitely varies for me. I feel like I need to switch up my writing "place" every so often, because if I get too bored somewhere I find it hard to be creative. Lately, I've honestly just been writing in my car before a shift at work. A little strange, but for whatever reason it works.
Taking a walk at lunchtime in a park nearby work opens my mind and hopefully gets the juices flowing.
Bird by Bird by Anne Lamott is supposed to be excellent also.
Public places for me!!!
Quiet and interesting rooms that feel welcoming. I've found some beautiful libraries, drab ones too that have done the trick. There's also a fair amount of low-key and cozy cafes in my city that frequent. I have a hard time getting much done at home--I'm too easily distracted.