Numbering Cells in Excel

Easiest way to do it: write the value 1 in A2, the click the cell, and you'll see a black square in the right-bottom corner of the cell highlight. Click this little square and hold the mouse button, press ctrl (see the mouse cursor change) and drag down all the way to cell A102.

I assume you mean you want to sort column and the numbers move when you sort?

You can create the numbers using the technique in the first answer (enter 1 and then ctrl-drag).

However to keep the numbers associated to the correct records when you sort you can then copy the range and paste special back with the values only.  Then when you sort the numbers will stay with the records you originally attached them to.

The answer markpx provided is correct and will give you that functionality.

by pasting-special-values-only (right click and choose "paste special" then select "values") you replace the formula that says "The cell above me, plus one" to a value - that will no longer change when cells are re-arranged. 

I agree with the first answer on this one, posted by middleman. 

I do this very often when creating a new sheet. I put the word "Reset" in cell A1 and number from A2 to about A10000. Then I hide the column. If I add rows, I just unhide it and re-number the cells.

This way if someone in my office ends up looking at the sheet and sorting the data, I can get back to where I left it.