You distractedly type in a whole series of labels, then realize that you meant them to go across a row, and not down a column. Rather than cut and paste them one at a time to their correct position, why not flip the column of data through 90 degrees using the Paste Special/Transpose option?
Start by selecting the column of labels or other data you want to transpose. You can click and drag or, if the column is very long, try this trick: Select the first cell in the column, hold down the shift key, and double-click on the lower border of the selected cell: Excel will extend the selection downward until it encounters an empty cell. Copy the selection, then select the leftmost of the cells where you would like the transposed labels to appear.
Now, the magic: Call up the Paste Special dialog with Ctrl+Alt+V (or command+control+V in macOS); hit E to select the Transpose option, bottom right, then Enter. As long as the source and destination areas don't overlap, you should see your cell entries spread across the sheet rather than down it.
Excel will only let you perform this trick using Copy, not Cut, so to delete the data from its original position, click once again in the first cell of the column, hold Shift and double-click the lower border of the cell to extend the selection, then hit Ctrl+Delete (just delete in macOS) to empty the cells.
Note that this trick also works the other way, for transposing a horizontal block of cells into a vertical one.