Hi Ray,
It sounds like you're trying to save your file as .mp3. This is often a reasonable choice, but you should be aware that mp3 is a lossy format. This means that when you encode audio to mp3, some of the audio accuracy may be lost. The benefit of lossy formats is that the files are much smaller, and the audio quality is often still good enough. So if file size isn't a problem, or you will be doing a lot of loading, editing, and saving of a file, then a lossless format such as .wav or .flac would be a better choice. But assuming you do want .mp3, then common bitrates for music range between 128 and 320, with 160 and 192 probably being the most popular choices. The 128 files will be smaller, but of lesser quality, the 320 files will be fairly close to lossless, but bigger. Personally I would choose Variable Bit Rate (VBR), and allow the encoder the full range (32-320 from memory). The encoder will choose a lower bitrate when the audio is simple, and a higher one when necessary. This results in a better tradeoff between size and quality than is possible with Constant Bit Rate (CBR).
Regarding Mono / Stereo / Joint / Force, for music you will probably get the best results with Joint (short for Joint Stereo), but Stereo is also a reasonable option.
Alex