I know. It can be scary. But if you're in a random location with others -- you already have a LOT in common.
Be totally comfortable going out by yourself. What I mean by this is do not have an agenda. If you do not meet someone while you are out, your night should not be ruined. Learn the beauty in time to yourself. I've had people approach me because I was content just chilling by myself.
Sit up straight -- no joke, countless people have commented on my posture. It mentally gives you a confidence boost in yourself.
Find an activity to do - go on a tour, find some sort of Airbnb experience. Activities bind people much faster than simple chats.
Compliments - if you like someone's outfit, say so. You can also snap a photo if you see a great shot and offer to send it to them. The smile it brings to people's faces is priceless.
Don't need the conversations to go forever. If you compliment someone, give it without agenda. And move on with your day.
People struggle in approaching each other. So bring something that makes this easy -- books are my favorite. It's a warm and easy invitation to others. As a bonus, you won't feel awkward being by yourself and it is a better use of time than scrolling on your phone.
I personally am very ok hanging out alone, thus I tend to not approach people. However, one of my more charming travel friends who is an expert at approaching has a process of identifying people sitting alone and who likely will not have a language barrier.
Make it a challenge to yourself: make eye contact with 5 strangers you're interested in, wave to 3 individuals. Quantify it and make it a personal goal.
When in a restaurant, sit at the bar instead of a table - this is more casual. Approaching is all about accessibility. It's easier to make a simple comment to someone sitting next to you rather than walking across the room.
Talk to the bartenders and your waiters - the locals are the best friends to make at any location you go to.
Exchange instagrams instead of numbers. There's less pressure for either of you to contact each other; plus you have built in prompts on social sites instead of having to come up with the topic and continue conversations.
Trust the universe will bring you people that you vibe with.
Probably the most fascinating thing about travel friends is how quickly you become very good friends. All you need are 30 fun minutes with someone, then next thing you know you are hanging out each day and have a friend for life.
The main theme here is to remain open and content with you first. The rest will come as it is supposed to.