If you know you will be visiting museums, zoos, aquariums or similar attractions while on vacation...join your local one before you go. Many times memberships transfer across the country. Sometimes you can get a reduced rate, other times you pay nothing.
Ask what the benefits are and tell your local one where you are going. They may even have hints for you.
Heading to a city with an upscale restaurant you are just dying to try? Then again, you know you really don't want to pay those kind of prices? Make a reservation for lunch. Many times lunch prices are half what you would pay for dinner.
Check out the visitors bureaus when you arrive in a new city. Ask for discounts, coupons or suggestions. Some cities have websites where you can print your own coupons before you leave home.