In short

• know the shortcuts
• use commands you typed previously
• switch between processes such as command line and editor efficiently

Keyboard shortcuts

• Shell uses readline library for reading your input
• Emacs style shortcuts by default

Configuring readline: You can configure readline to use Vi style shortcuts, too. How?

Completion — avoid typing (and typos)

• Pressing the TAB key attempts to complete the current word.
• Bash attempts completion on variables ($..), usernames (~..), hostnames (@..), commands, aliases, functions, and file names.
• To just see possible completions hit M-? (or TAB twice), and to insert all possible completions hit M-*.

Completion: Some commands add their own completion hints to bash. For example, try typing git sta and hit TAB twice. How do they do it, or at least, where is this documented?

Re-use command lines, history

There is plenty of customization on how Bash keeps a record of the previous commands, see https://www.shellhacks.com/tune-command-line-history-bash/. To use the command history, it is usually enough to remember three key shortcuts,

Also ‘HISTORY EXPANSION’ is available, see man bash.

Which environment variable controls how many previous commands Bash keeps in the history, and which controls how many are saved to a file when the shell exits?

Process/job control

Usually one has at least two programs running simultaneously, an interactive shell session and a text editor. One can switch between these either by using some sort of windowing system or just switch active process using CTRL-z for suspending the current process, and commands fg, bg, and jobs.

Job control: Which do you prefer, window manager, multiplexing terminal emulator (tmux), or just single terminal and job control? What are the relative benefits and drawbacks of different solutions?