1. Check for any danger to yourself or person you are treating.
2. Check for any responses from the person i.e. movement, speech etc.
3. Check airway is clear.
4. Check the person is breathing.
5. Check for any severe bleeding or severe burns.
6. Check for any broken bones.
7. Get help ASAP 911, 999 or whatever your emergency number is.
These are the basics when dealing with an First aid situation, there is no need to check for circulation, if the person is breathing regularly then they will have a circulation. If at any point you find a problem "Stop" and deal with that problem then carry on.
A good well stocked First Aid kit is always handy to have too, but no medication just in case the person you are dealing with is allergic to any medication and they can't tell you.