There are so many aspects to this, even for amateurs. I'd suggest that to some extent (not totally, of course) it is a matter of good manners. Are you gonna make money because you're using what someone else created and owns? Then have the manners to ask that person if it's okay. This can be done legalistically or informally--it's up to the user to do it the right way.

Examples: my group wanted to record "The world turned upside down." We wrote directly to the author, Leon Rosselson, and asked for permission. He was very willing to give it. A short exchange of letters resulted in a payment to him of royalties. No problem. That, I call the informal way. When we went looking for permission to record something written by one of Peter, Paul & Mary, it was a different story. We dealt with publishers and publishers' agents, some of whom had ceased to exist years ago. But in the end we got permission and paid royalties. That, I call the legalistic way.

As for performing, there's an approach I call "common sense." If you perform a copyright tune for profit, someone should pay the copyright owner. This may be covered by a license granted to the venue, or a deal between the presenter and a rights organization like ASCAP (American Society of Composers, Author & Publishers) or SOCAN (Society of Canadian Authors & Composers). Otherwise, your own conscience, common sense, and decency will probably give you the right direction.