Much of first aid is common sense, and people are almost certain to learn some elements as they go through their life (such as knowing to apply an adhesive bandage to a small cut on a finger).

However, effective life-saving first aid requires hands-on training by experts, especially where it relates to potentially fatal illnesses and injuries, such as those that require Cardiopulmonary resuscitation (CPR), as the procedures may be invasive, and carry a risk of further injury to the patient - which the ‘3 aims’ of first aid above, clearly try to avoid.

As with any training, it is more useful if it occurs before an actual emergency, although in many countries, emergency ambulance dispatchers will give basic first aid instructions over the phone while the ambulance is on its way.

To be adequately trained, a person must attend a course (hopefully leading to a qualification recognized in their country), but then, due to regular changes in procedures and protocols, based on updated clinical knowledge, must attend regular refresher courses or re-certification in order to ensure they are doing the best for their patient (and in some countries, to minimise the chance of being held liable for further injury or deterioration).

Training in first aid is often available through community organizations such as the Red Cross and St. John Ambulance, or through commercial providers, who will train people for a fee. This commercial training is most common for training of employees to perform first aid in their workplace. Many community organizations, such as the ones above, also provide a commercial service, which complements their community programs.