If you are parking on a street there are a small number of motorbike parking spots. Other wise just take a parking spot. And I would park in the middle of the spot other wise some one might try to squeeze in with you. As far as paying , yes you do have to pay just like a car. Scooters are NOT exempt. They are just like a car. And stick your payment on your dash, seat or windshield.
Now if you park in a garage the you still pay the same as a car ( But I do know some garages charge less for a motorbike monthly parking pass then they do for a cars monthly parking pass) but you are aloud to park in corners and areas were they were not able to make another spot for a car. Like at the front or end of a row. So to be safe as far as garages go just ask the attendant.
I saw a device made for the Portland pass @ Ptown scooters. It is a little less likely to blow away or sprout legs.
What is the feeling about sidewalk parking like bicycles? Not everywhere, but when is it appropriate? I've seen it downtown quite a bit. Is there a size of scooter that, above which it isn't acceptable?