Is a sample chapter any chapter?

First 3 chapters only. Ever.

Yep. First three.

Unless the agent only asked for 1. Then it's the first.

Depends upon whether it's fiction or nonfiction.

For fiction, it's always starts with page one and goes on from there.

For nonfiction, it depends. Many nonfiction books have stand-alone chapters, where you don't have to read in order to understand the chapter. For example, each chapter of EQUINE LIABILITY deals with a different topic. Reading them out of order doesn't do a thing to the book. For EQUINE LIABILITY, I submitted the first chapter, then two chapters chosen by the fact that they were more or less done. I think it ended up chapters six and eleven, but I'm no longer sure.

For a nonfiction book that flows in order, something like a history, or a book that builds upon concepts, like some math texts, it will be the first three chapters.

Best of luck,

Jim Clark-Dawe