Although it varies a little depending on which command shell you’re using, you can recall previous commands and then edit them before pressing enter.
|Press this…||…to do this|
|ctrlA||jump to start of line|
|ctrlE||jump to end of line|
|← and →||run both ways along the line|
On the Mac, in Terminal, if you hold down option ⌥ and click with the mouse on a character on the line, the cursor will jump to that position on the line.