A common mistake I see people make is holding down the left or right arrow key to get to the start or end of the command-line. Instead, try these shortcuts:
Control+A to jump to the start of the command-line
Control+E to jump to the end of the command-line
Knowing these two shortcuts will help you with about 80% of the stuff you edit on the command-line.
Two other useful shortcuts to know are:
Option+Right Arrow to jump forward one word (or Alt-Right Arrow)
Option+Left Arrow to jump back one word (or Alt-Left Arrow)
What’s also great is these shortcuts work anywhere that has editable text including a browser’s URL bar and a text field on a webpage.