Quick, clean, and to the point

Copy selected cells

Windows shortcut 
Mac shortcut 

Copy puts everything on the clipboard: text, formulas, formatting, borders, fills, etc. Use Paste Special to selectively paste only parts of what was copied.

On the Mac, Ctrl + C also works

Related videos

The videos below show how this shortcut can be used.
This video shows how to stop Excel from changing cell references when you want an exact copy of a formula in a different cell.
Pivot Tables are fantastic tools for summarizing data, but you can also use formulas to build your own summaries using functions like COUNTIF and SUMIF. See how in this 3 minute video.
In this video, we'll look at how to create a line chart in Excel to plot historical, 30-year mortgage interest rates.
In this video, we look at how to simulate a random drawing to pick winners in a contest with Excel, using the RAND and RANK functions together.
In this video, we'll look at how to create formulas that reference cells on different worksheets, or even in different workbooks