If you want to play your iPod through your stereo speakers, all you have to do is use a 3.5 mm headphone jack to connect the iPod to an adaptor cable. The Monster high performance iCable for iPod will offer the highest sound quality, but any adaptor should work.
Before connecting your iPod to your stereo, turn the iPod’s volume down at least half way so you don’t accidentally overdrive your speakers. You can then adjust the volume and using your iPod to do that will keep the sound quality better than using your stereo volume, but you can also adjust your stereo volume to get more sound if you need to.