The way the relevant parts of sectioning commands work is exemplified by the way the `\chapter` command uses the counter secnumdepth (described in Appendix C of the LaTeX manual):

1. put something in the `aux` file, which will appear in the `toc`;
2. if the secnumdepth counter is greater than or equal to zero, increase the counter for the chapter and write it out.
3. write the chapter title.
Other sectioning commands are similar, but with other values used in the test.

So a simple way to get headings of funny ‘sections’ such as prefaces in the table of contents is to use the counter:

```\setcounter{secnumdepth}{-1}
\chapter{Preface}
```
Unfortunately, you have to set secnumdepth back to its usual value (which is 2 in the standard styles) before you do any ‘section’ which you want to be numbered.

Similar settings are made, automatically, in the LaTeX book class by the `\frontmatter` and `\backmatter` commands.

The value of the counter tocdepth controls which headings will be finally printed in the table of contents; it is normally set in the preamble and is a constant for the document. The package tocvsec2 package takes the tedium out of changing the secnumdepth and/or the tocdepth counter values at any point in the body of the document; the commands (respectively) `\setsecnumdepth` and `\settocdepth` make the changes based on the name of the sectional unit (chapter, section, etc.).

The KOMA-Script classes have commands `\addchap` and `\addled`, which work like `\chapter` and `\section` but aren’t numbered. The memoir class incorporates the facilities of all three of the abstract, tocbibind and tocvsec2 packages.