If you are wanting to increment the same amount over a range, the easiest way to do this is use paste special. You can add, subtract, multiply, and divide.
1. Find an empty cell, enter the amount you want to change, hit enter, and then copy the cell using ctrl-v or copy from the menu bar.
2. Select the range you want to modify, right click, and choose "Paste Special".
3. Select one of the math options.
That's it. The one drawback is if you select a cell that is blank, it will be populated with a number (0 or the number you are adding/subtracting).
Otherwise, you can create a short vba script to go through each cell of the range.
Skaven13