I occasionally find it helpful to get out of the studio and visit a local café. I often bring my sketchbook and watch people while I try to get some new ideas. Sometimes it works, sometimes you just want to eat a biscuit and relax...But I guess that's also ok.
My favorite sketchbook comes from Bookbinders. I love that it's a refill book, so that you can keep the beautiful cover when you run out of pages.