The 10 bits of advice listed below have changed my life. These are the things I personally do every single day/throughout the day. As a result - generally - my anxiety day to day is under control and I am able to live the way I want to and do the things I want to do. There is a lot of advice already available about dealing with anxiety, but much of that won't be overly helpful for people on the autism spectrum. I wanted to share my personal strategies with you because I hope they may be useful to you too.
1. Finding out lots of information so I know what to expect
I need to know what is going on pretty much all of the time. In situations that I don't have a lot of control over (for example, when I'm out of the house, shopping, at work, at a social gathering...), I prefer to know as much as possible about "who-what-where-why-when-how." When I have this information, I can use it to decide whether or not I will participate. If it sounds manageable, I'll be more inclined to participate and enjoy it. If it doesn't sound manageable, I'll decline and probably end up avoiding the likely outcome which would be a meltdown/shutdown. Knowledge is power, as they say.
Having lots of information about something before I agree or disagree to participate makes me feel like I have a bit of control. That sense of control is very important.