How do you not dissociate?

The physical stuff is probably the most effective and immediate. I've also found talking aloud to work. I'll just start speaking exactly what's going on. (Granted, around other people, you have to speak internally.)

When I have had the presence of mind to do it, I've actually talked to "myselves" aloud often in life when I go into a panic, as if other parts of me could hear me and help me, even though I never came to understand that meant I had DID. That practice, speaking aloud to myself with the definite purpose of calling on another part of myself, a stronger part better equipped to handle something, should have pointed me toward multiplicity but it didn't.

Now that I know about the DID, talking is effective because my others really do want to help me keep from losing it. My danger wasn't so much switching as it was dissociating, fuzzing out, going away from the present. Sometimes, of course, dissociating was a deliberate choice and an advantage, helping me to partially escape from a really boring work presentation or a family event that I didn't want to be fully present for.

I'm making a distinction between dissociation that leads to fuzzing reality but no switch and switching to another alter with a loss of time. If you're talking about switching, eventually you're going to have to be in some communication with alters who are triggered to switch in so you can work things out and prevent inappropriate switching. Talking aloud to your alters may be able to start that process, depending on your system.

I tend to think of grounding yourself physically as an effective short-term solution for dissociation with or without time loss, and communication as a long-term solution. The former is the band-aid, the latter is the cure.