Do a Topic Search on the Uniden forum for Fire Tone Out, this topic has been discussed extensively there. There is also an article in the August 2006 Monitoring Times about this very topic.
In a nutshell there are several methods to find tones. The most accessible is to record the tone outs and decode them with audio software such as Audition.
If you let us know what department you are looking for we may already have the tone on file in the CARMA database.
As for receiving only your department's calls you can use a Uniden BC15, 996, 396 or 330 as a tone out receiver or purchase and outfit a Plectron, Reach, Motorola or other receiver with the proper tone and freqs.