If you need to send a file to Support to be printed to the plotter, here are some things you might want to consider.
The Plotters that we have at Scient are HP ink-jet plotters. They use Cyan, Magenta, Yellow, and Black ink cartridges (CMYK). Adjust your colors accordingly. RGB seems to print fine though.
If you create a file that uses fonts that are not standard issue (this usually pertains to Visual Designers), you should be aware that the person printing your file might not have those fonts and, depending on the program, your fonts will either be substituted or faked, neither of which will probably look exactly the way you intended it.
In most graphics programs, there is usually an option to collect fonts for output. In Illustrator, it is under Type and called Collect Fonts for Output. In Quark it is under Utilities and called Collect Fonts for Output. These methods will place the fonts you are using in a folder which you can send with your file to be printed.
Unfortunately, this would only help a user who is printing your file is she has the same computer platform as you do. Mac and PC fonts donŐt work on the otherŐs platform.
Luckily, if you are using Adobe Illustrator, there is an option called Create Outlines. It will turn any text you have selected into editable postscript vectors. Only do this on a copy of your work as the fonts will no longer be fonts after you do this. Anyone with Illustrator can now print your file just as you want it even if they do not have the fonts you used.

Also in Adobe Illustrator there is an option when you are saving a file to include placed images. These are the Gifs, EPS files, and whatever you placed within your Illustrator document. If you do not embed these objects when you save your file, you would also have to remember to send them when you send that document to be printed or there will just be blank space where they were supposed to go.

Aside from all these choices, you could also save your document as an Acrobat PDF. You typically need the full version of Acrobat to do this. Some of AdobeŐs high-end graphics programs (Illustrator and Photoshop for instance) have built-in PDF creation ability.
Once you create a PDF of your work it should be able to be printed by most anyone.
DonŐt worry about converting your artwork to CMYK. RGB will print fine and will most likely produce the closest colors to what you are see on your screen (which is RGB).