I don't usually book places in advance unless it is like the Colisseum in Rome.
For restaurants to have dinner, I usually ask at the hotel desk. Or I just look around as I am traveling through because except in the case of really famous restaurants, it is better just to see what's there when it is meal time.
AAA can book some. I also just put it in a search engine and see what is available. Often times a city will have a page developed for such things.
I usually look up the local tourist information office. I check it online before we leave, and then when we arrive in a new place, that's one of the first places we visit. They have maps! They also have good advice. We've often discovered nice local restaurants from the tourist folks. My husband asks them where they are eating lunch. It works. 
rtind123
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Portugal?
Some tourists drop everything in the hands of their favorite travel agency in their own city. I book my own flights through the airline websites. For a new country I prefer to arrive during day or at least early evening hours. This way I have more transportation choices.
For a middle of the night arrival I will book a cheap room ahead of time. This way I have a place to direct the taxi to. For day time arrivals I may wing it and hunt up a room. I prefer to choose an area with restaurants, bars, malls and shops easy to walk to. I do research some possible places to stay at ahead of time so I don't end up wandering around aimlessly.
If a restaurant needs a prior reservation ahead of time this place would not have any interest to me - not with my money! If someone else wants to pay I will gladly eat there. If a cheap hotel has a breakfast buffet I will start the day eating there first. I have never had much of a problem finding a place to eat in around 30 countries just walking around or asking for a cheap place to eat.
Just stumbled across an archery match in Paro city centre (Bhutan) this afternoon - absolute gold!!
I dont like joining tour groups when travelling. Most of the places and activities you can go by yourself without over-charged.
For example, Hong Kong Ferry Tour. It charges $180 HKD while you can take a normal ferry price at less than $5 HKD. Ok, the Ferry Tour ferry is decorated for tourists but that's really not neccessary.
I usually search on internet because it is too much easy and fast. There are some sites where you can find all activities like local restaurant, hotel, car for rental and many more!
As far as restaurants, what I have done in the past with pretty good success is ask someone like a hotel desk clerk or bartender where they would take their wife or girlfriend for a special occasion like a birthday or anniversary.