If you need to layoff employees, make sure the criteria you use is both consistent and business-related. There is a huge potential for accusations of discrimination when laying off employees.
Also, note the differences between a 'lay-off' and 'termination'.
A lay-off is done for business reasons and it means the elimination of a position(s) that will not be re-opened again (or at least for a very long time).
A termination is a specific action against a specific employee. The position will be filled again.