I started @ 2.5 to 3.5 (1 minute intervals) Always a 15.0 incline. Then increased speed as it became easier at those speeds. The best part is according to the machine its over 500cals in 30 minutes, even though it may be inaccurate, its a badass feeling of accomplishment + I think it does good on calves, The last I go for the max speed i can tolerate non-stop brutal 2-3 minutes. Its hell.
I usually do around 30-45 min of rough cardio after each workout..hey you get a pump in your calves haha
I lift 3-4 times a week and just do 15 mins of hiit on my off days. its working great so far. my diet is pretty clean except for sundays it gets a little "dirty" ;-)
Awesome dude short cardio sessions after weights does wonders for me...