When performing a first aid and CPR what things do you do before you can carry out with the treatmeant?

You should always check the scene for hazards that may be threatening to your safety, obtain consent from the victim (or victim's guardian if a child) if able, and put the appropriate barriers (gloves, breathing masks, etc.) in place before administering any type of first aid. If you are a lay person (rather than a 'professional' rescuer) you should also consider whether you are ready and willing to get involved. You are not obligated to become involved, but you are obligated to remain involved once you start administering first aid until you become exhausted or endangered, or transfer care to someone with equal or superior skill.