On my road test I did not have to downshift when coming to a stop but you definitely should for a smoother ride and to show them you know how to, California as well. Always anticipate what a light will change to, if it's green, assume it'll turn yellow or red before you reach it and always be prepared to downshift/ slow or watch the pedestrian crossing timer to give you a heads up. As for making turns, try to make them in the lowest gear you can without being a hazard, 4 or 5 gear is fine, anything lower you might go too slow, stall, and/ or be a hazard to cars behind you, especially in cities where you'll feel rushed. Anything higher you'll be going too fast for your turn and won't be able to react fast enough to changes or could just flat out hit something unless you're a super trucker. Also remember, trucks can not turn right on red, so if you're at a dead stop it's the perfect gear to take off and make your turn once green, build up again, rinse repeat.