Sometimes just pressing keys until one does what I want works, but this feels rather unelegant. Is there an easier way of finding out what keys do what?
When you're in the agenda buffer try
C-h m which should give an overview of the current mode, show which commands are available and list their keybindings.
There are a few other ways to access the built in documentation (as found in the manual) that you might want to explore.
kc-modeshows you, on demand, at any time, all of the keys you can use then, along with the commands they are bound to.
kc-auto-modedoes the same as
kc-mode, but it also shows you automatically all of the keys you can use after you use a prefix key (e.g.
C-x), along with their commands.
Even better: use Icicles key completion. (Key See behavior is a simplified version of this.) In addition to what KC shows you, you can immediately get complete help on any key/command shown - its full doc string is shown in buffer