Smile like no tomorrow, keep a good expression as long as you need that appology.
Be relax and comfortable. Show them that you're comfortable of being forgiven. Be worth forgiven and you shall be forgiven.
Go with a gift, something your friend loves much. Bribe???
Find someone and go together. Never go alone, you might lose confidence.
Take a step at a time. If they don't want to talk, leave them and assure them that you're going to be there whenever they are prepared to talk.
If you're forgiven, even a part, show your happiness. Jump, hug, laugh, cry, like a baby to show your emotions.
If they refuse to forgive you, do not oppose or hate them. Love them more. Be kind and sensible. Don't talk bad.