Hi Anthony - my fave place to stand for the MK parades is anywhere between the Country Bear Jamboree in Frontierland and The Diamond Horseshoe Saloon in Liberty Square - near the CBJ, is a raised garden bed with trees - so you can even sit whilst you wait and you have shade too.
In all parks, before they put up the rope, you will see the white tape on the ground to show where the ropes will go - stand by that and check that you have a clear view both ways, remembering that other people will be either side of you. Make sure by looking at the parade route on the guidemaps that you are not standing in an area designated for wheelchairs (the symbol is a red square with a P and a w/chair) - you will be moved on.
In MGM, we always end up near "Sounds Dangerous", but if you can grab a bench on Hollywood Boulevard really early that would be a great spot to be.
In Animal Kingdom, steer clear of areas where paths meet the parade route from other 'lands' as you will get a surge of people in those areas at the last minute.
A spot recommended by a CM who posts on the DIS is between the fruit stand and Kilimanjaro Safaris. He says after the parade passes, you may be able to alk onto the Kilimanjaro Safari and then see the parade again after you get off the ride !!!(It starts and ends at the service gate near the Safari entrance.) I'm putting this to the test next visit!