You can use the AutoFill handle to quickly drag a series into existence. You can drag days of the week, months of the year, or a numerical series — you can even create your own custom series.

When working in Excel, you may wish to see the formulas in use on your worksheet to help you track down an error, or to see which cells are dependent upon other cells.
To toggle the display of formulas on a sheet:

In the Tools menu, click Options.
On the View tab, in the Windows options area, [...]

You can use data validation to restrict the type of information allowed in a given cell (or cells). You can also specify a range of valid data for numerical, time or date values, and even text length. In addition, you can use data validation to limit data to a predefined list of acceptable items.
To set [...]

You can use VLOOKUP or HLOOKUP to find corresponding information in a list of data, either vertically (VLOOKUP) or horizontally (HLOOKUP).
The VLOOKUP function scans vertically down the leftmost column of data, looking for a match to the input you provide. Upon finding a match, VLOOKUP returns a value from the given row, corresponding to a [...]

Excel gives you the ability to combine text from multiple cells into a single destination cell.
For example, if you have a cell that contains a first name and another cell that contains a last name, you can combine those cells together and also include arbitrary strings of characters such as a spaces (“ ”), or [...]