There is no magic to starting a 450.....just unlock the car (even if it is unlocked already, the immobilizer engages after five minutes, giving rise to the weird symbol in the LCD display).
Once unlocked, put it in neutral with your foot on the brake pedal (the car should ALWAYS and I mean always) be parked in Reverse, or it will eventually roll away when the handbrake fails to hold it. This car will not shift from R to N to forward gears unless the footbrake is on during the shifting maneuver. Doing it without the brake on gives a nice "0" in the LCD.
Also, the ignition interlock (the equivalent of the steering lock on a conventional car, on the smart it locks the shifter in "R") will not work unless the shifter is left in "R" when the car is locked.
Once in N, press the footbrake and start the car. On the diesel at least, all you need to do is flick the key to start and release it immediately; the car decides how long the starter is needed.