Keyboard shortcuts are really useful for saving time. Here's a summary for MAC.
Command + A - Select all
Command + B - Bold
Command + C - Copy
Command + D - Fill
Command + F - Find
Command + G - Find next
Command + H - Hide
Command + I - Italic
Command + K - Insert hyperlink
Command + N - New workbook
Command + O - Open
Command + P - Print
Command + S - Save
Command + T - Open a new tab
Command + U - Underline
Command + V - Paste
Command + W - Close
Command + X - Cut
Command + Y - Redo
Command + Z - Undo
Here's a summary for PC.
Ctrl + A - Select all
Ctrl + B - Bold
Ctrl + C - Copy
Ctrl + D - Fill
Ctrl + F - Find
Ctrl + G - Find next
Ctrl + H - Replace
Ctrl + I - Italic
Ctrl + K - Insert hyperlink
Ctrl + N - New workbook
Ctrl + O - Open
Ctrl + P - Print
Ctrl + S - Save
Ctrl + U - Underline
Ctrl + V - Paste
Ctrl + W - Close
Ctrl + X - Cut
Ctrl + Y - Redo
Ctrl + Z - Undo