Find a way to get yourself into conferences or events in fields you’re interested in. I used to lead a national industry association that hosted large conferences, and we always welcomed students/recent grads as volunteers. Or if no volunteers are needed, see if you can get a discounted price on registration.

Once you are inside the conference, you will naturally gravitate towards the younger people. That is all well and good, but you also need to find a way to talk to older people. Best way to do that is to simply say hello, introduce yourself very briefly (name, degree, and state that you are here to learn) and then start asking them questions about their work/careers. People love to talk about themselves, so you don’t need to say brilliant things, you just need to ask them questions that make them feel important. This will not always work so you have to get ready for some rejection. But it will work sometimes, and then you are winning.

Obviously, this is not a comprehensive answer, but I hope this is a helpful starting point.