If you're typing a large amount of text that you would prefer to have shown
in separate rows instead of one long row, instead of having to figure out
when to hit enter to keep it even, use the justify command afterwards. Type
all of the text in first cell, select the range you wish to limit your text
width and several rows down. Prior to 2007, go to Edit, Fill, Justify and it
will be separated into individual entries on consecutive rows. In 2007,
click the fill button in the Editing section of the Home tab and choose
Justify.
If you did not select enough rows to handle the data, the range will be
extented down, if there is data in those cells, it will be overwritten.
If instead, you were wanting to type only 5 characters in column A and then
have it automatically move to column B, you could instead type all of the
data in A and then use text to columns to separate the data into individual
cells. The Text to Columns command is on the Data menu prior to '07 and on
the Data tab, Data tools section in '07.