I see many comments about putting yourself out there or common activity.
I've tried all that. I put myself out there, talked with everyone I came across during the day, and tried different activity clubs, even activist clubs.
The issue is most people you meet in a club will stick in the club. You can have one on one hang out but it doesn't become your personal group. You still feel lonely when this club breaks, or when you're not at the club. It also doesn't feel like YOUR friends when the context always involve the club...the existing hierarchy. etc.
I've met many people and like many have suggested, I did all of them. I was friendly, and chatty, and cared about learning more about this new friend. And we have a great time.
But when you hit them up after a week or so, they won't come out. They may not even text you back. But most of the time, they'll be busy. And after a few tries, it pretty much ends there for MAJORITY.
I have made great friends and stayed in touch with few, but most were a dud that never stuck around.
It usually goes like this:
Meeting them
Having a great chat, common hobbies, beliefs, you name it, joking, fun time!
Exchange contact
Hit them up
5a. They come out
5b. They don't come out, try again later.
People who don't come out usually will say they're busy or they're meeting up with their friends on that day.
People who do come out usually will stick to a one-on-one basis, so every time you see them, you meet them one on one. Which can be fun. I had some good fun sports time with this set up. But imagine having 5 friends... that's 5 separate one-on-one hangout... it's time consuming.
A common issue with both outcomes is... these people don't invite you to their existing social circle. You become a separate entity to fit into their existing schedule, so their chances of squeezing extra time for you is low. Even if they do meet you, it sticks with this one-on-one basis and you never expand your social circle.
Best outcome: One-on-one, but meeting each friend to build the friendship on a one-on-one basis is tough on their schedule as well as yours. It doesn't last.
Worst outcome: Never hear them again
Painful outcome: When you finally click with someone, and they hangout with you a few times...then they move away to another country for work or study and you lose this friend...