Use menus. The menus are really handy for discovery. Many I see disable them (the menu-bar-mode), but it doesn't take up more than about a line, and I go to it to discover what interesting bits a mode has or to find some functionality I use less often and forgot the keybinding to it. I do also use which-key-mode, and there is always M-x apropos & the completion, but menu is a nice companion to these stuff.