First is the ABCs of CPR and the three C's of assistance. A is for Airway, B is for Breathing, and C is for Circulation. The 3 C's stand for Check, Call, Care. There is also a D that stands for defibrillation but only if you have an AED around.
Approach the individual and check them for conciousness. Call to them in a loud voice to see if they are okay or responsive.
Next, call 911 for emergency and stay on the line with the operator. They will assist you in performing CPR on the individual; however, we will go over it anyways.
Now, check for any signs of breathing by placing your ear over the individual's mouth and look for slight rising and lowering of the chest to indicate breathing as well as listening for breaths as well. This is checking the airway.
Now, get out the CPR face mask if you have one and get it ready. Tilt the individual's head back to open the airway by pushing the chin upwards with your 2 fingers.
Next comes the breathing for the individual. While having the head tilted back, perform 2 rescue breaths into the mask or just by mouth to mouth by pinching the nose and giving 2 breaths into the person. Do this while watching the chest rise and lower when giving the breaths.
Now, check for circulation by checking the carotid pulse or radial pulse if you have been trained on how to do this. If not and there are no possible signs of life then start chest compressions on the individual. This is done by sitting straight up over the individual with shoulders straight, arms almost locked and placing one hand in the center of the person's chest while interlocking fingers with the other hand on top and pressing downward with your body weight approximately 2 inches downward. See image for more info.
Keep this up until paramedics arrive on scene to take over with defibrillators. I really hope this helps in saving someones life and teaching others about the importance of knowing how to perform CPR to help others.