Depends on aircraft type, but any flying club should be able to show you. Generally, the key points are:
Check that prop is NOT live (mags off, etc.)
Generally you can push on prop (close to hub, one hand either side), leading edges of wing, and anywhere it doesn't say "no push". Obviously don't push on any control surfaces. Front edges are generally good.
I suspect the reason you have been told not to push down on the rear fuselage to turn the aircraft is because it will then pivot around the main wheels, taking some rubber off the tyres at the same time, which is not a good idea.
On many aircraft there are handles in front of the tail, on the fuselage, so you can push or lift on these.
Safety is the main consideration. Be aware of things like sloping ground and always always double check that the prop's not live.
You are best off having two or more people pushing the aircraft, with one person allocated as in charge, to direct everyone. Brief the others they can shout "stop" loudly at any time they are not happy.