do this alot when logging with my father (even done it by myself somtimes, ssshhhhh).
ive had two close calls-
my little brother cut the hinge off! (stupid, inexperienced saw operator.) small tree slid off the stump stuck in the ground and i pushed it over anyways.
temperatures about -10, 3ft snow pack. dad pushed one over for me. it brushed past another tree 30ft away in the direction of fall. it broke a limb off on the way by and a peice of limb about 2ft long and 4inches diameter came back and hit him in the shoulder! we found where it broke of 50ft in the air on the tree standing tree, not the falling one! gotta call that one a freak accident.
anything you push a tree over with should have a fops/rops/ops. and no, i wont tell you how to push a tree over by yourself without wedges, cause its just stupid.