You don't have to put a car in neutral (using the gear lever) to start it, as long as you put your foot down on the clutch. This disengages the gear so you can start it without the car kangarooing forward and stalling. I am talking, of course, about cars with a manual gearbox. Having driven an automatic car only once (and hating it), I can't speak knowledgeably about that.
In any case, to start the car, you put the key in the ignition and turn it (or these days, apparently, put an electronic card in a slot and push a button).