I told my very close friends, and I tend to always have at least one person who knows around all the time. I can usually tell if I'm going to switch, and thankfully it's not a daily thing most of the time. If I feel dissociative, I tell my friend, and tell them to get me out of that situation if I look like I've switched, because most of my alters can't hold in the fact that they're not me for more than 10 min. It's worked okay so far, though it can lead to some rough nights (my boyfriend had to lock himself and my not-so-nice alter in his bedroom at his moms house one night so the rest of our friends and his mother wouldn't think I was losing it), and it's usually a rough time on the person who's with me because they don't fully understand, but I haven't been publicly humiliated yet.

But yeah, my advice is take yourself out of the triggering situation, and into a new environment where the body's safe and your alter feels comfortable. Safety first than comfort though, as I learned the hard way a few times now.