Clearing Cells

You can easily remove the contents of a cell by selecting it and pressing the Delete key.
Using the Delete key only removes the contents of the cells and does not remove any formatting.
Never use the spacebar to clear cells as it actually adds a space to the cell which is then also impossible to find later.
Alternatively you can use (Home tab, Editing Group)(Clear drop-down) to display a sub menu of possible items to remove.

Clear All - The contents, the formatting and any cell comments are all removed.
Clear Formats - Removes just the formats from the selected cells, leaving the contents and comments the same.
Clear Contents - Removes just the contents from the selected cells, leaving the formats and comments the same. This is the same as pressing the Delete key.
Clear Comments and Notes - Removes just the comments, leaving the formats and contents the same.
Clear Hyperlinks -
Remove Hyperlinks -
An alternative and sometimes a quicker method of removing formatting is to drag and drop an adjacent cell which has no formatting applied.

You can multiply a cell range by a given number. Enter the number in a cell and copy it. Select (Edit > Paste Special) and select "multiply" and click OK.
You can decrease all the values in a range by 10 percent, type 0.9 in a cell. Copy the cell and select (Edit > Paste Special) and click multiply.
You can enter 32,000 characters into a cell however if you try to copy the entire sheet then any cells containing more than 255 characters will be truncated. To avoid truncation, copy the cells of the source sheet to the destination instead of copying the sheet as a whole.
Remember that a cell being left blank or empty is not the same as a cell being equal to zero as the result of a formula, or entering a zero in a cell (which are both values).