Nikon D300 Manual Available for Download
Trust me, this 15.5 MB PDF instruction document for the Nikon D300 is a fantastic read, all 448 pages of it – be sure to download it!
Both English Language (printable and non-printable) and Spanish (non-printable) versions of the D300 owner operation guide can be downloaded.
The user guide, which is titled "Nikon D300 Guide to Digital Photography – Camera Owner's Manual is available in printable (not available at the time of writing) and non-printable version (the 15.5 MB Acrobat document that I referred to).

For copyright purposes, the printable version of the Adobe Acrobat PDF document requires you to input your camera serial number and agree to a license, while the non-printable version doesn't. You'll get the following dialog box if you try to print the password-protected, non-printable document:

The guide discusses the features of the D300 and how to use the camera, for instance, on page 369, there's a list of accessories that can be plugged into the remote terminal. The Phottix Cleon N8, a hybrid RF (radio frequency) wireless shutter release (trigger), is an example of such an accessory.