Not sure about which tutorial it may be...
1. Get a great waveform visualizer
2. Grab your reference track and play it! And it better be the BEST quality possible, a lossless .WAV or Apple's equivalent. Best option is to buy a SACD (used mostly... Super Audio Compact Disc, another lost format), or online from someone that specifically sells lossless audio files (don't skip this step).
For rock, you can't do better than a remastered "Owner of a Lonely Heart" by YES (do I like that song? not really... but the mix is perfect). For Dance/House: "American Dream" by Jakatta (same reason). Jazz/Ballad/Vocal heavy: "Black Crow" by Diana Krall (a perfect song...)
3. Analyze it... peaks, width, consistency with style of music, balance... I could go on for hours. But, that's what it takes. Hours spent with ears open. And then going to listen to the same song on mp3, vinyl, cassette if it were possible... perfect reference headphones (Sony MDR7506) and shitty dime store emergency earbuds... what's there and what's lost? Learning how to hear the difference is INVALUABLE. Can't stress that enough.
or
Get IZotope mastering software, watch guide on applying reference tracks, learn how and why the software works, and apply. Monthly $$, purchasing the software... $$$$
Sort of a PtP shortcut.