How do I surrender in battle?

get out your French army knife and take out the white flag

You could pretend to surrender but really your plan is to see who's in charge, what their plans are and pull an escape and end those plans, to be dramatic, let some of your comrads die, as a writer of course, not the character doing it on purpose

Stub your pinky toe.

There's a bunch of ways to do it, if you care to elaborate more about the specific scenario, you might get more than the typical "white flag" answer.

Dangerous, but typically you'd lay down your arms and waive a white flag.

If that's wrong, just ask someone from France. They'll know. .

Surrender and have your enemies gather. Then slaughter them all!!!

With great sincerity, yell "Ouch! Stop doing that. I don't wanna play anymore. I'm tellin' your ma!"

traditionally you wave a white flag of some sort.

It depends on the era, the nationality and the context.

Depends on the type of battle. And against who, need more details.

You must never surrender.

White flag