When making a left turn, you should:

Left turn procedure: position your vehicle in the leftmost lane that permits left turns (which may be a dedicated turn lane or the leftmost through lane); signal at least 100 feet in advance (more on highways); come to a stop if required or yield to oncoming traffic if turning across opposite-direction traffic on a green light without arrow; complete the turn into the leftmost lane of the new road's same direction. Crossing over multiple lanes during the turn is illegal and dangerous — complete the turn cleanly into one lane, then change lanes after the turn if needed. Green-arrow signals give protected left turns where oncoming traffic is stopped; round green lights still require yielding to oncoming traffic.