Tour Guide Books (Frommers, Fodors, Rick Steves, etc.).... don't bring them with you as they are too heavy to carry around all day and contain more info than you need. And, it makes it difficult to take photos while holding those books!
I photocopy the pages that I'm interested in and bring those with me. Each day, I take only the pages that I'll need for siteseeing that day then throw them away at the end of the day. I have the books at home for reference when putting together photo albums yet haven't burdened myself with additional weight during my trip! And my load gets lighter as the trip progresses.
I also make a list for each location of restaurants that I want to try. That way, I'm never without a 'recommended' restaurant.