A safe and very effective method to use is "bug busting" http://www.chc.org/index.cfm
. All you need is a conditioner and a good lice comb. Wet hair and apply lots of conditioner, use the lice comb to remove all the lice, repeat every 2-3 days for 2 weeks. The first session should remove all the adult lice but you need to keep doing it to get all the ones that are still to hatch.
It takes some time to comb through the hair thoroughly but you aren't using any nasty chemicals and it works.