Yes keep the handbrake on at junctions. The idea behind it is that if someone crashes into the back of you, you dont panic, lift your feet off the pedals and jolt forward into the car in front - this would definitely happen in an automatic if you released the footbrake!
Also you would want to put in neutral if you were expecting to stop for more than a few seconds. You should never have it in drive with the handbrake on, as this does produce excessive wear on the brakes because the wheels are trying to move forward.
If you are stopping for a second or so, you should be fine with just the footbrake, as you would be in a manual.
I don't drive and never have driven an automatic by the way. But I do know how they work.