Another way is to go online in the forums and search for a thread pertaining to your city. Usually there is already a thread about where you can practice in your area and even if it's a few years old the practice spots still remain the same. There might be a few new ones that pop up every now and than but usually bboys stick to the same areas. Of course bboying has the freedom to practice almost anywhere, whether it be actual dance studios or concrete. I once danced in the parking lot at night time under the street lights but that floor was too rough to do anything serious. Still managed to do it though and that's the key point. But yah, you can message bboys and try to find their practice areas and just do your thing, no one will judge.
Especially when starting it can be very intimidating, you're very self-conscious about how you look at what you do. However if you're not a cocky ass bitch and actual try your hardest there ain't nothing nobody can say about you. Most people will actually praise your for your efforts because at one point in time they were in a very similar position you were in. Eventually you'll talk with someone and you'll click and you can learn from each other to become better bboys.
One of the main reason you want to go to these practice sessions, and why many do, is because you actually get better faster. There's someone there who's better than you there and you can watch what they do and learn what you're doing wrong. So even without talking or anything and just being there you can learn a lot of things. Of course if you get to talking you'll learn even more and you'll have a more rich and more powerful experience.
My personal experience with this was pretty good but I know of a few that didn't really like it. Sometimes you just have to give it some time before you become accustomed to it. Think about it, instead of having to practice in you're garage or basement, which is probably shitty, you can practice in a well lit studio or nice concrete with plenty of open space and people to show you tips on how to improve. And the best thing about it too is IT'S FUCKING FREE! You don't have to pay a goddamn penny to anybody. Probably the easiest way to get good fast is through these practice sessions.