this video is pretty good, the more open your notch is pretty good
Product Demo Videos ECHO Chain Saw Carving Video How To | ECHO USA
there are some others
you need to adjust for natural lean and figure where the top will land
there are plunge cut techniques and wedge use, i prefer to put ropes in the top or near the top for pulling, the higher you get it the more leverage you have, my wedges i use mostly for keeping cuts open so my saw doesnt bind
be sure to leave a hinge, this will control the tree as it falls, the more open your notch is the long your hinge will hold, when your notch closes your hinge will break, sometimes this is good, sometimes this is not, depending where you want you butt to end up
beware using machines to pull on ropes, you dont want to break your rope
and make good knots, a good knot needs to do two things, it needs to hold, and it needs to come out when youre done with it
and _never_ cut from a ladder, if you need to cut limbs in the air use the right tools or hire a professional
most companies bid tree work based on time involved, putting trees on the ground and leaving the mess for you to deal with means less equipment on the site and less guys to do it so you can get some pretty good deals
one more note
you cant make a good notch with a dull saw