There are several ways to adjust column width in Excel:
Select at least one cell in each of the columns you want to adjust, then select the funtion from the menu bar. In Excel 2007, it's Home/Cells/Format/Column Width. If you selected one column, or if all of the columns you selected are the same width, it will show the current width in the window. Type the new width you want then press Enter or click OK.
Another way to access that same window from the Excel 2007 menu is to type Alt+H O W.
The rest of these methods are good for any version of Excel. In the column heading, the box above the top cell of the column containing the column letter, position the cursor on the right edge of the box. The cursor should change to a short vertical line with arrows pointing left and right. Press and hold the left mouse button. You will see the current column width. While continuting to press the mouse button, move the mouse left or right to your desired column width, then release the button.
If you select several entire columns then do the previous procedure on any of the selected columns, all of the selected columns will have the new column width when you release the mouse button. To select an entire column you click on the column heading. To select several, you can either position the mouse in the column heading, press and hold the left mouse button as you move the cursor horizontally to the last column you want to select, then release the button, or after selecting the first column click on the headings of additional columns while pressing Ctrl.
To automatically resize a column to fit the cell of the column with the most contents, double click the right edge of the column's heading.
If you select several entire columns then double click the right edge of the heading of any one of them, each of the selected columns will be fitted to its own widest cell.