This might apply to previous versions of Word as well, but I came across some interesting tidbits related to resizing columns in Word 2007.
When you move the mouse in between two columns and get the column resize cursor, if you resize a column, in the middle of the table, it makes the next column wider as the previous column shrinks. If you’d rather resize the whole table, hold the Shift key as you resize.
Every now and then you might find that just the one cell resizes rather than the whole column – in this case, make sure the cell isn’t selected – when one or more cells are selected, the resizing only affects the selected cells.