Try and avoid touristy restaurants and instead go down a few blocks and eat where the locals do.
Travel during the low-peak season and avoid traveling during the summer and around holidays.
Have a picnic instead of eating out. You can experience the local culture’s day-to-day activities, as well, by shopping in their grocery stores.
Don't buy any expensive souvenirs, or any for that matter. Instead, take a photo or get a post card
Bring a water bottle. Paying for pop and water accumulates really fast, and that money can get you another night in a hostel every week
What's more important to you, time or money? If the answer is money, book a flight with a layover option instead of direct, they are always cheaper.
Get familiar with the cities bus system. It is the cheapest and best way for transportation; except for walking of course!
Talk to locals. Make friends. These people know all the secrets about their hometown, they may tell you or even invite you to stay with them!