Sit and ponder. Contemplate, it is a lost art. Take the time to think, quietly, about nothing, if need be. Analyze things and just wonder. Try and figure out for yourself how things work, even if the internet can tell you. Enjoy your surroundings, take in conversations, basque in the light. Observe the light. Just be cognizant of your surroundings, of the world, and enjoy it.
You learn a lot from eavesdropping, and learn more from sitting quietly. I learned, that when doing ethnographic research, that if your informant answers your question, sit quietly, and do not say a word. The silence that develops between the two of you will make them feel uncomfortable. They will feel the need to fill that void, and elaborate more on the answer they just gave. Trust me, the best skill a writer can have is observation and the patience to listen.
Bars are great character development locations. Coffee shops are great spots to watch first dates. No character is too insane–trust me on this one, I am qualified to make this assessment. The best characters, have, well, character. Townie bars are great places to observe.
Above all else, remember, a story best told is one experienced.