1. Find the comfy armchair in the corner and park your bum in it. If it looks like it's falling apart a bit, even better: it'll be more comfortable. Usually they'll have a socket near to them, which means you don't have a time limit. Plug your phone or laptop in and settle in for a few hours. It's comfy, it's warm, and you can actually get things done.
2. If you like, open up that laptop or bury yourself in a book, but if you're any sort of writer, I suggest people-watching. People tend to view coffee shops as public places that are sort of private as well: everyone sort of lets a few of their usual walls down while they concentrate on their books. That means more things to watch and more things to turn into stories.
3. Try not to stare at people too obviously. People don't like being observed, and you don't want their attention on you while your attention is on them. You're doing the people-watching here. Also, they might try to talk to you and who wants that?
4. Ignore the weird art on the walls. Nine times out of ten, they’ll look like they were done by a five year old and will most likely be selling for over a hundred dollars. It’ll just make you feel a mixture of infuriation and personal failure. And don’t listen to that one asshole that tries to defend them as art. He’s probably the one who did them.
4. People are interesting if you let them be. Don’t look at them and immediately put them into the boxes they appear to belong in. Where did the girl that just picked up the pumpkin spice get that sweater? Who is she talking to? What did she do this morning? Give her a story. Use the little details you pick up to flesh it out.
5. People are walking stories: the lines on their faces, the cat hair on their coats, the length of their hair, their glasses, what they’re carrying with them, everything. Everything tells you something more about them. Whether or not you’re right is immaterial: you’re telling the story. Unless you want to be a journalist, in which case you have to ask. Which makes it awkward.
6. Be nice to the baristas. You are a complete and utter ass if you aren’t. They’re giving people coffee all day. Be friendly; be the customer they remember because you were nice to them. Also, tip them, because they're probably making pennies and you can afford to pay another dollar for your coffee.