HIIT cardio advice

Hi, What is the best way to utilise HIIT cardio to boost Test/HGH production and EQ? Is it actually the best method of cardio to improve these? Or is a 50/60% jog-brisk walk more effective?

A lot of the info on the web seems to be conficting in how to actually do HIIT, is 30 sec sprint/90 sec rest the best way? Or should I go all out and stop when I begin to fatigue from 90-100% effort? Then rest until I can give all-out effort again?

Also how many intervals should be done for a noob, 8 sets?

Any help greatly appreciated