There are meet-in and meet-up groups you can find in your area. If you do a google search for meetin or meetup (two different organizations), they list a bunch of activities that you can sign up for IRL (not online). Typically, you'll meet people with similar interests, which is one way to get to know people in order to make friends. You can generally ask the leader of those groups questions about the venue, such as how many people will be attending, or whether there are equal males and females, etc. Depending on your social preferences, you can find groups that are the right size and comfort levels for you.
It would really depend on what kind of friends you are looking for, also. Are you looking for friends with similar interests? Are you looking for close friends who can comfort you and vice versa? Are you looking to make healthier friends than what you've had in the past? Writing a list down will help you determine the place you'll find such friends.
For instance, if you're looking for friends you can go hiking with, you'd typically find a group that hikes (or even a hiking class), and start from there.
But if you're looking for more emotional support, that typically takes time. You can meet those kinds of friends anywhere, but in general, people take their time before diving into a supportive friendship - probably a year or longer, sometimes less, depending. That said, if you really could use emotional support soon, then support groups might be one of the best ways to meet friends.
If you're looking for healthier friends than what you've had before, you have to ask yourself what qualities you'd like in a friend, and how you overlooked those (negative) qualities in the past. Sometimes therapy/counseling can help with building boundaries, assertiveness skills, self-esteem, and detection of red flags in order to avoid toxic relationships. Generally, meeting up in groups only (not one on one) might be the safest first step before forming close relationships right after toxic breakups.
If you're looking for a professional network, where your friends typically have the same work-related interests as you, attending local conventions, symposia, and conferences are wonderful ways to meet people. For instance, if your hobbies are really work-related, like research or tech stuff, then you can attend the local conferences that relate to your topics of interests or your field of study. Students aspiring to become professionals often do this for networking purposes; they may find potential peers who can befriend them for advice or peer mentorship, or they may find professional mentors who are willing to hire them as interns or research assistants.
Even introducing yourself to your neighbors offers some level of social support. They may not be your close friends, but they are someone familiar you can do small talk with. You can suggest a mixer to your apartment manager, or you can offer to host an apartment mixer in the lobby of your apartment complex. Mixers can be as simple as a potluck to as extravagent as hiring a DJ or other entertainers as well as catering.
Relationships take time to build, including friendships. Many people have established a strong social network throughout their high school and college years, but there are the rest of us who weren't so lucky for one reason or another. For those of us who have not had strong social connections, or who lost their connections, rebuilding new connections may seem tough. But even people with strong social connections find themselves moving to new locations or moving apart from old connections at some point in their lives. In essence, everyone struggles with making new friends at some point in their lives. Some are more extroverted, which makes it easier to be the initiator of friendships and invites. Others are more introverted and/or have little disposable income to spend time out finding and maintaining friends who are more affluent. Many suggestions I've made above do tend to cater to extroverts, but there are enough extroverts who will reach out to us introverts at the right place and right time. It's a matter of finding out what those right places at right times are - for us.
Hopefully these suggestions help.
