On our recent trip to Europe we knew ahead of time that our two biggest expenses were going to be lodging and food throughout the five countries we were planning to visit. Since we were planning to be gone for six weeks it would be an enormous expense to feed three off us three times a day. So with some advanced planning we decided that we were absolutely not going to be eating out every night.
Instead we decided to take advantage of the dining and kitchen areas at the hostels or hotels we were going to be staying in when we did not stay in an apartment. Also when we booked all of our lodging we found out where a supermarket or grocery store was close by. It saved us a ton of money to buy a few days worth of groceries and cook meals, even preparing snacks ahead of time for our sight-seeing or hiking trips.