I'm the same; when I do go out I focus on the reason why I'm there - I do it as quickly as possible, and I avoid people.
The last time I was out, I went bra shopping - and I spent an hour trying on bras (cos I have lost a lot of weight and I didn't know my size anymore), but since I was in a booth it was fine. If I go shopping I grab the items I like really fast, then stay in the dressing room for as long as I have to.

When I've been out shopping with someone else, I've had several anxiety attacks when they go "Ooooh look at this!" and spend five minutes trying to decide if they should purchase it or not; clothes, food, movies, whatever.

Noises and such really get to me, I get really irritated and I just feel like leaving. I have to zone out completely to be able to cope with it.