Working in an operating theatre for almost 2 years has taught me that CPR is largely quite useless, and mouth to mouth is rarely needed. If a patient gets to the point where they NEED life saving skills, they need a defib, and a doctor. Little else will help them.
Regarding mouth-to-mouth, ensure that the CPR situation actually
requires it. Mainly, MtM is ultimately a useless waste of breath, time and CPR has proven more successful with just chest compressions (not to mention the person may have an unbeknowst dangerous virus like TB or MRSA, which is very common in Asian/African people recently returning from abroad - we get kids in our hospital all the time with such illnesses)
If a person has had a HEART ATTACK, forget MtM; the problem is that the heart is in fibrillation (so it's having a dubstep party in someone's chest, basically), and requires a regular beat (breathing into them does nothing much, as the fibrillation means the body can't
do anything with that air). Do chest compressions and await help. Heart attacks are very fast killers; if nothing else it will keep YOU calm (or the people with you), and at least make you feel as if you helped. (that's grim, but it's ultimately the truth... a dead heart is a dead heart)
If a person is DROWNING or has suffered an OVERDOSE, make sure you do MtM. This is vital, as their airway is likely physically closed, or obstructed. Do chest compressions as well. If you are concerned that the person has a virus or condition you do not wish to catch, poke a hole in a plastic bag (careful not to smother them with it), or carry around a pocket face mask so you can safely administer MtM.
If you are unsure (i.e. you simply find someone lying there), do your ABCs (airway, breathing, circulation) and just call for help and start chest compressions.
Good article though, the stuff about stings and bites and whatnot was really useful!