1. Be prepared to fight a long battle. Adult lice and immature lice are pretty easy to get rid of, but their eggs are much harder to get rid of, and it is with these nits that the most problems crop up. People can think that they are rid of lice, but then get another case of lice from just a couple of eggs. Constant vigilance will be necessary to win this battle.
2. Buy a quality lice treatment (also known as a pediculicide). You should be able to buy one over the counter at a local drug store. You should also get a quality nit comb (a normal comb is not fine enough to remove nits and lice from hair); a flea comb for pets may also be used.
3. Apply the lice treatment to the hair. Be sure to follow the treatment instructions, especially regarding the duration the treatment should be left on the hair and how it should be removed. You may need to buy another bottle to treat someone with very long hair.
4. Remove the treatment from the hair as directed. Note that you should not shampoo or condition the hair with normal shampoo or conditioner for 1-2 days following treatment.
5. Make sure the person with the lice then changes into clean clothes following the treatment.
6. Wait 8-12 hours (or as directed). Use the nit comb to remove the dead lice (and any ones still living) from the hair. If you find lots of live lice at this point, you may need a more effective pediculicide; contact your doctor for a recommendation.
7. Comb the hair with the nit comb and carefully check the scalp of the infested person every 2-3 days. Continue this process for 2 or 3 weeks to ensure that all of the lice are gone. Most lice treatments require a second application after about 10 days to kill any lice that may have hatched since the initial treatment.
8. Clean all of the infected person's contaminated belongings: clothes, towels, and bedding will need to be washed in hot water, and their mattress and room vacuumed thoroughly. Use the hottest setting on the dryer and dry for the longest time you can without harming the fabric.
9. Or you could...
10. Buy a cheap conditioner from your local supermarket. Also get a nit comb.
11. Rub the conditioner into the person's hair. Make sure you use enough conditioner.
12. Slide the nit comb through the hair quite hardly (to make sure you get the nits out) Make sure you do this until you are sure you have done enough.
13. Go round the hair with your fingers just to double check.
14. Finally, wash out your hair, making sure there is no more conditioner in the hair.