Rehearse it

10.  Rehearse it

Briefly rehearse what you want to say.  Writing it down can help order your thoughts and communicate clearly to the one you have harmed. 
(To be continued.)

No excuses

9.  No excuses

Remember the comic Flip Wilson and his famous line “The devil made me do it”.  Unfortunately, Flip was wrong.  The only thing we can truly control is ourselves.  When apologizing make no excuses.   
(To be continued.)

Own it

8.  Own it

By your demeanor, tone of voice and eye contact show the seriousness with which you regard what you did to the offended party.  If appropriate, extend your hand or perhaps touch their shoulder to further communicate that you understand the gravity of your failure.
(To be continued.)