Laser safety is a very important topic ! I cannot give you all the rules in a little message, but you can see them on http://repairfaq.ece.drexel.edu/sam/lasercc2.htm#cc2saf.
You also can buy a very usefull book :Laser Safety Management (Ken Barat ; Taylor&Francis Ed.)
DO NOT use your laser if you are not fully advised of its working rules ! It is not very difficult : use it as you were a professional !