In order for an LDP document to be accepted by the LDP, it must be licensed to conform to the "LICENSE REQUIREMENTS" section of the LDP Manifesto located at http://www.linuxdoc.org/manifesto.html. As an author, you may retain the copyright and add other restrictions (for example, you must approve any translations or derivative works).
We recommend using the GNU Free Documentation License (GFDL) or the Open Publication License (OPL) without options A and B. If you choose, you can get DocBook markups of both the GNU GPL and the GNU FDL from the GNOME Documentation Project. You can then merely include the license in its entirety in your document. Due to its length, you may just want to provide a link to the source.
If you choose to use a boilerplate copyright, simply copy it into your source code under a section called "Copyright and Licenses" or similar. Also include a copyright statement of your own (since you still own it). If you are a new maintainer of an already-existing HOWTO, you must include the previous copyright statements of the previous author(s) and the dates they maintained that document.
You'll note that the licensing for the LDP Author Guide requires notification to the author of any derivative works or translations. I also explicitly place any source code (aside from the SGML the Guide was written in) under the GPL. If your HOWTO includes bits of source code that you want others to use, you may do the same.