Useful knowledge alert!

Revere blogs about a couple of recent articles that suggest new procedures for cardio-pulmonary resuscitation: if a person has collapsed with circulation failure (because they have had a heart attack, been electrocuted or drowned) it seems more important for survival to keep up circulation than inflating the lungs. So, if you are alone, don't bother with mouth-to-mouth, just keep compressing that chest.
If you don't know how to perform chest compression, get in contact with your nearest Red Cross centre, they regularly give courses in first aid. (CPR is visible and dramatic, but I think the most important thing taught in these courses is the habit to go up to people lying on the ground and check on them instead of just stepping over them.)