Couchsurfing is a social platform which allow locals to meet travelers and its probably the best way to meet people when you are new in a city. Before getting conected to other travelers, you need to create a profile, where you can write your interest, traveled countries and ask or offer accomodation as well. It´s a great idea and a great way to get to know a city with the eyes of a local.
If you want to increase your chances of getting a couch via Couchsurfing check my article Tips to get a couch
2. Social media groups
The times of traveling around the world with just a map and a compass are over and internet is getting every day more common and important between travelers. Most social networks have travel related groups, where users post about their travel plans, ideas and itineraries. It´s a great way to meet other travelers before arriving in a new spot and plan activities where you don´t know anyone and don´t want to go alone.
3. Dorms and hostel facilities
Every backpacker knows that you have to stay in a dorm if you want to meet other people. Most hostels offer dorms where travelers get their privacy in a shared space and are able to meet other backapckers. Many hostels offer as well common rooms, bars or even a kitchen, where travelers can interact with other travelers, get a drink together or cook a meal.
4. Free or non free tours
Almost every European and American city has free tours, where travelers pay what they think that the tour worth. These kind of tours are an excellent choice for meeting other backpackers on a budget, crossing other travelers from your home country and getting at the same time a small lesson of history in the place you are.
5. Pub crawls
Pub crawls are fun and very popular between youth. In this kind of tour you will pay a certain amount of money and a group of guides will take you and other travelers to different bars, give you all kinds of different and locals drinks and shots and party the whole night. It´s perfect for travelers trying to meet other party travelers and have a good time.