There seems to be so many answers and guidance when your child with an ASD is younger but as they age its scary because the support dwindles away. I read a great article in Autism Digest by Chantal Sicile-Kira about creating Independence and want to share some of my favorite highlights.
The first is self-regulation- this is something that is taught and does not always come easy to a child on the spectrum. Some key points to remember in developing this skill:

My son trusts me more than any other person. In the heat of the moment, he may want to doubt, but I remind him "If you can't trust me, who can you trust? I gave birth to you and no one will fight more for your right to be treated with respect." He can't articulate why, but I think I understand what is at the core of his trust. I plan to share my philosophy with his teachers.
D trusts me because he knows I will be fair:
I lobby for what is right and just-whichever side that may be.
?If I am wrong about something, I will admit it.
?He can talk and I will listen.

Autism has helped me have more appreciation in the value of a good friendship.
Growing up, we moved around a few times so I never truly felt rooted in school and thus I wasn’t a ‘popular’ kid. I tended to hover on the outer fringe of many social circles.
Throughout my teenage years many friends came and went. Some friendships were good, others bad, though I certainly didn’t see it at the time.