I had the exact same question. I got my liciense in 1983 when there was no need to take a motorcyle safety course. Last summer a friend of mine decided to buy a bike, so I took the couse with him. I asked one of the instructors the same thing... this is waht he said;
The general rule from a safety point of view is 1st gear, clutch in, left foot down and right foot on brake... why??? Well 1st gear so you can get out of the way quickly if need be and right foot on brake so that the brake light is always glowing regardless of what your right hand is doing. Watch yourself, I did, and found I tend to use my right hand do a lot of little things like scratch my leg or adjust my helmet while waiting at a stop.
Based on that theory, if you are riding 2 up or when the road is uneven and/or balance or stability is a concern,just be sure to use the front brake to keep the brake light lit... then you meet the safety concerns. You should be able to roll on throttle with palm, thumb and pinky finger while holding the brake with the other three, just as you do when you blip the throttle for downshifting, so starting on a hill with both feet down should be no probs without having to give up stabilty