Reading? Reading about writing, reading other people's writing, reading my own stuff with an editorial eye--heck, I'll read nearly anything. Any magazine within reach at a doctor's office, a newspaper, a booklet--some are better examples of good writing than others, or course. But I recently picked up some really good advice from a very poorly organized book.
Staring out the window? I read recently (I cannot remember where) that Woody Allen can't work in a room with a window. I don't know that it's true. I can't work in a room without one. I once wrote all the publication materials for a nonprofit organization, where I had a cubicle in the middle of the building. Not a window within my line of sight. Then, they shuffled us around and I worked in a cubby by a big window. I figure my production during that period (I was later moved back, doggone it) was up at least 30 percent.
I now work in a home office on the second floor, looking out into the tree tops lining our backyard. I see the sparrows on the telephone wires, squirrels on the fence, cat on the shed roof. Without that view to stop and stare it, I don't know that I'd ever get anything done. Instead of distracting me, it gives my mind a nature break and re-energizes me as I sort through my ideas.
So sit, read, and stare a bit. More about staring out the window later. I am convinced they'll all help you become a better writer.