How do you maintain friendships? What’s the hack?

Seriously, how do you all do it? I have some friends but I wanna know how to maintain, keep or deepen the friendships. I have lost so many over the years, these are my new found friends. I have no idea how to do small talks nor do I know how to continue conversations….. are there any tips and tricks that work for you? Should I warn them before hand that I have adhd and if so, what do you usually tell them? Like a list of things to be aware first.