In any user interface element that accepts text, there are a set of text editing keyboard shortcuts that work in almost every application. Most are not listed in menus or only in certain applications.
Here’s a great link that documents most of the shortcuts. Note that the document is missing a few newer ones and there are a few that have changed since it was published, but this is the best resource I’ve found.
Here’s a subset of them that I find particularly useful.
|⌥ ⌫||Delete the previous word (if you make a typing mistake and it spans multiple words, this is a really quick way to delete what you just typed)|
|⌥⇡ or ⌥⇣||Move cursor to beginning or end of paragraph|
|⌘⇡ or ⌘⇣||Move cursor to beginning or end of document|
|⇧⇡ or ⇧⇣||Select upwards/downwards one line
|⌥⇧⇡ or ⌥⇧⇣||Select upwards/downwards one paragraph|
|⌘⇧⇡ or ⌘⇧⇣||Select upwards/downwards to beginning/end of document|
|⌃⇡ or ⌃⇣||Scroll one page up or down (most keyboards don't have dedicated keys for this anymore)|
|⌃A||Move to beginning of line (super useful in Terminal)
|⌃E||Move to end of line|