Social skills and tactics

Over the years I’ve read an awful lot of self help books and most of them were just a waste of money. But I’d like to think there are some gems that I just haven’t found yet.

So, can any of you recommend any books about social communication or social tactics/strategy? Ones that are actually useful?

Alternatively, what tactics and tricks have you learned to use to keep in touch with friends, make new friends or just reduce friction when dealing with other humans?