How do you store your Newtonian Scopes?

undercover ,outside on the mount pointing north

When in use on the mount, either pointing North or to the zenith. When not in use upright. Long storage times do nothing to any of it if the right precautions are taken (such sealing as to prevent the ingress of little critters, no damp and cover the front end with a sturdy cotton cloth to allow the innard to "breath").

Mine sits with a cap and a plastic bag over the end pointed straight up.  I only do that to minimize floor space so that it can sit in a corner of my office.   If you really want to minimize dust on the mirrors, there's a pretty good argument to be made that storing the scope horizontally is your best bet.  That's how I park my remote 20".  Dust is heavier than air so keeping the mirrors oriented with surfaces vertical (and the secondary pointed shiny-side down) will minimize the amount of dust that will collect over time.

John

I keep my 6" atsrograph in a Pelican 1660 case, with dessicants. The case is big and takes up a lot of space in my den, but I know that my (a bit expensive) OTA is safe and dry all the time. Also, the case has enough space for the camera, guidescope and filterwheel.