Re: Parking Problem
Total,
Well, that depends on the aircraft and how it's built. Typically you're OK to push on the prop hub (checking that mags are off and key is out).
Presuming all-metal airplanes, other locations for low-wings are usually the leading edge of the wing along a line of chord-wise rivets (implies a structural member which the rivets are attached to), but do it reasonably close to the root (say, no more than halfway, as oppposed to out on the wingtip). On high-wing airplanes you are almost always safe to push on the struts.
Rag and tube is a bit different and really requires showing someone.
Hope that helps,
Pitts2112