Start up from a bootable CD, DVD, or USB thumb drive (such as OS X install media). Start up to either Apple Hardware Test or Apple Diagnostics, depending on which Mac you're using. Option-D. Start up to either Apple Hardware Test or Apple Diagnostics over the Internet.
You have a position in every situation you face... if you donât know it.. then it is simply a position swinging in the air. Nevertheless, when others who understand strategy meet you... they will know your strategic position and will be ready to overtake you in any challenge with them.
1 A good spotter shares the responsibility of spotting equally. It is easier and safer to work as a team when spotting.  Spotters should stand in a balanced position, holding hands up in a ready position. The spotter's focus must be on the participant.