In Guitar Tracks Pro 3 - is zero dB the optimal level?

I've used PSP Vintage Meter, I've used Inspector, I've used a bunch of plug-ins to see where my mixes "sit" in the audio spectrum. I guess my question is simple enough - when mixing, you want everything to have it's place - is zero dB on the fader (fader set to display peak values) the maximum target? I've read up on Bob Katz' mastering system, but I'm still green enough not to know where 0 dBFS is on Cakewalk's products. Is that 0 dB on the meter or is it peaking out as close to the clip indicators as possible?