Do you have hobbies and interests? If so, hop on Google and search for MeetUps in your areas. When you find one, go to it and do that activity with other people. This is a practically fail proof plan because it sets you up to do something that you like doing with other people that also like that thing… which gives you a built in conversation topic.

While you’re there, talk to everyone for a few minutes. Next time there’s a meet up, go back. Don’t put pressure on any one person but, after you’ve been a few times, you’ll recognize and enjoy the company of other regulars and, voila, friends.

• Stop declining when people invite you to stuff.
• Stop being picky about activities/food/music/etc.
• Be vigilant/safe, yet open minded, open to new experiences, spontaneous.
• Plan trips and events, both budget friendly and splurgy, then actually commit to doing them.
• Smile and laugh n shit.
• Compliment people, thank people, be considerate to others even if it's not always reciprocated.
• When it is reciprocated, gravitate more towards that person, and gravitate slowly away from people who don't seem to appreciate you.

You have to be ok with believing that you're not annoying others when talking about yourself and asking about them. And you have to do it in a not-creepy way. I haven't quite figured it out yet.

Put yourself 'out there' more. Friends are very unlikely to fall into your lap. Don't shy away from get togethers that you usually would and you'll likely find people that you gel with. Work is a good place to make friends and you can branch out from there. Pre-established friend groups are also nice to get in on. Other than that, regular activities are good (gym, classes, volunteering etc) there are nice people everywhere (just avoid the dicks)

Hobbies and pursuing them. Like board games? Join the local game night! Like sailing? Join a sailing club and attend! Like football? Join a local football team. Like thinking and debating? Join a Sceptic Society!

It’s hard to be the new kid, it never changes with age, but you just need a few shared experiences and people start thinking of you as part of the tribe.

Hobby clubs, fitness groups, volunteering, specific interest events. Personally, I plan to attend more local events. There are some upcoming local events that pique my interests.

Volunteer

My partner and I recently moved to an entirely new city. It’s in a region I’ve lived in before, but a different city.

We found a meet up group called “ 20 something’s meetup” and went to a few events. We found some people we really enjoyed and invited them to a few other events, and still regularly attend the group as a whole. The internet has done a lot of work for us.

Exposure pretty much. Meaning get out there, join some groups, talk with people at work or anywhere you spend a good amount of time at, and see who you connect with. Be curious but not invasive.

I think we make too much of a deal about making friends as adults. Kids are so much easier in this: “Want to be my friend?”, “Sure!”
I’m guilty about this as well, too shy and awkward to just make friends. But I believe most people would be happy to have a new friend if the other made the first move. We’re all just so socially awkward about these things.

Anyway, if anyone wants a friend, I’ll be your friend :)

I realize this doesn’t really answer the question. Best way is to be open and eager to make friends, I suppose?

Search for a community of people with similar interests where you live. E.g. something you like doing for a hobby.

Board game meetups and clubs work great

There’s tons of good comments here. Mine will echo some! I just wanted to share my experience.

I have three hobbies that I’ve explored since moving to a new city in my 30s - axe throwing, pinball, and making music.

I found a local axe league and joined for a season. One season has become four :) The people I throw axes with are wonderful and varied. While we may not have crossed paths otherwise, they’re fine folks and I consider many my friends.

I went to a local pinball bar for a casual tournament and have been going every other week since. It a supportive community and I’ve had a great time learning about the games and learning about the folks on my various teams.

I answered a Craigslist ad for a band looking for another member. We’ve clicked quite well and have practices together, go out together, record together, and even play shows!

Exploring your own hobbies in some sort of structured way might be a good step in your own quest :) Good luck!

I started playing disk golf which has started to build up some sort of social network. Doing a physical activity with other people really seems to work.

prison

I don't think my answer will be popular but I found a really nice LGBT welcoming lefty church and the people I've met there are the delight of my heart. It can happen.

Offer potato

Join your local Marxist organization.

Buy a boat.

Volunteer. All the best people do.

I saw a shirt sometime saying something like "At a certain age, you have to give birth to new friends." While it wasn't exactly like that, we made a lot of friends through our kids and their schoolmates or sports activities.

Bars on Friday nights, volunteering, or church. The Masons if you're male and want to meet intellectuals.