If you've never done HIIT before, it's probably best to start off a bit slower than every other day. I would recommend 1 or 2 times per week. What I normally recommend to people to start off with is to do something like this:
5 minutes warm up
5 cycles of 60 seconds high intensity, 60 to 120 seconds of low intensity
5 minutes cool down
Don't go overboard with the high intensity at the start. Push yourself more than you normally would to begin getting used to a slight higher intensity. As it gets easier, bump the intensity up slightly. For the low intensity interval, slow down to a point where your heart rate and breathing rate can come down.
After a while, you can increase the intensity, shorten the work intervals, and decrease the recovery intervals. Overall, your HIIT workouts should be shorter in comparison to a steady state cardio workout, just remember, the higher the intensity, the shorter the overall workout usually is.
You can pretty much do HIIT using any equipment, but I usually recommend not doing it on a treadmill, as the faster you go, or the more incline you put on, the more dangerous it can be. If you want to run, I ususally suggest going outside or using a running track if you have access to one.
