Although psychologically disturbing, head lice can be removed and no diseases can be transmitted by them.
The following video by the American Academy of Dermatology deals with the practical information to find and treat head lice and is summarized by the following points:
Examining the hair for the presence of head lice (nits) and where they are most likely to be found
How to make the difference between nits and dandruff
Applying the medicated shampoo, and rinsing it after leaving it on for a few minutes. (please read directions which vary from one product to another)
The use of a lice comb to remove the treated nits
Hair care following the treatment
Care of the surroundings following the treatment
The transmission of head lice from one individual to another