Square_peg is correct. A twelve inch tree is just too large for a small forest axe. Great axe, but it's more of a bushcrafting axe. Just think that if it takes 3 minutes for an experienced user to cut through a tree with a felling axe it will take approximately 6 minutes with a boy's and 9 with a large hatchet like the small forest axe. And generally this will take more energy as well.
There was an old manual from a competition axeman. I forget the name of it right now but I'm sure someone will remember it. It had the best illustrations and info on notch patterns that I can remember. Strangely there is very little information out there on this and it is one of the most important things.
I have not read through this all but it has similar illustrations:
http://www.thedump.scoutscan.com/scoutaxe.pdf
With bucking you see how this advocates starting forehand and hitting top, bottom, middle. The reason you do this is because you either want the toe or heel slightly outside of the cut, as this keeps the axe from sticking so much. Or in other words, you always want to create a chip with one open side to make it easier. If you cut top and then middle there is more likelihood of getting the axe stuck since the chip is basically locked in from the bottom. And generally the heel is the easiest to get a cut so it will be better for hard wood.
You can also alternate between backhand and forehand to get chips rather than a whole plate as the above method shows. Forehand bottom, backhand bottom, backhand top, forehand top, forehand middle, backhand middle is one example. Personally I think this is the safest method as well. Hitting the bottom hit first means there is more material when you start and have to judge distance more, and forehand top after the backhand means you have a little more control when the chip is popped.
You can experiment to find what works best for you. Chips or plates depends on the situation really. Just remember that you have to be lifting the chip, so sometimes when you're learning you may have to try hitting the same spot twice. You may also want to learn bucking by rough bucking rather than standing on top of the log as it is safer. Keep in mind that you will have to make the cut nearly twice as wide to get through though.
As well, once you're experienced enough you want to aim for 50 degree cuts at the start. This is because of the way the axe cuts, after each chip in a successive spot (each layer essentially) you have to decrease the angle by a few degrees or you are at risk of a glancing strike.
In felling the practise is basically the same. Farside, nearside, middle, or backwards to this. Going for chips is the way to go here, mainly for safety reasons (preventing barberchairs by keeping an enforced hinge), but due to the nature of felling you want a straight cut on the bottom, almost parallel to the ground and across the grain, so it is much harder to cut deep. This means you will have to hit twice on this swing much more often than with bucking.
Professional competitions are a fair bit different but they give you an idea of what you need to do. Standing block is different due to the fact you don't need a real hinge, you don't want to swing up like that in felling. But it's still good information as there are so few good video tutorials.
https://www.youtube.com/watch?v=GQZacqMrA9w
https://www.youtube.com/watch?v=rb9fWu7JES8
And remember what Kochanski says about axes. Often women do better in training because they focus on aim and pattern while the men think they can power their way through it. Bucking can be good practise as it is very dangerous to try and power through. I would also recommend going through small trees like birch and work your way up to the 8-12 inch trees.
If you're going with the small forest axe you'll want to rough buck standing from the side. Otherwise you can find cheap vintage axes if you want to try a full-sized axe.
Good luck.
