As for leg pressure, for some reason my dad has this idea that you use the inside leg to turn. Don't ask me where he even heard that. I use outside leg to turn, unless I want the hips to turn away from my leg in a turn, like in barrels. So suffice to say, my dad has been training his horse to move away from inside pressure. Totally backwards for me, but he got mad when I was doing it "my" way. Sooo...with MY horse, I'm going to teach her MY way, and he can do whatever he wants with his LOL. (Perhaps there are trainers out there that teach this way, or maybe I am completely backwards, but it just seems so unnatural the way he is doing it. It makes more sense to me that if you want the horse to move AWAY from pressure, and you are turning to the left, you use your right foot.)
"Your" way is correct. However, what your dad may be thinking of (and has perhaps misinterpreted) is that you do use your inside leg at the girth, as a sort of passive "post" for the horse to bend around. Also, there are times when you would use your inside leg more aggressively, such as when the horse is dropping the inside shoulder and/or not bending well through the ribcage. And, just to confuse things further, dressage riders turn the horse by creating a very active bend through the ribcage with the inside leg, pushing the ribs out (this is where you are still correct in that the horse should move away from pressure) and catching and containing that outward movement of the ribcage with the outside rein (inside rein is a flexing rein, only) as the outside rein bends the shoulder into (or through) the turn. The outside leg is behind the girth as needed to keep the haunches on the line of the bend as well, but the outside leg is not as active as the inside leg. This is because the riders leg effects the horse's rear leg on that same side. And in order for a horse to bend
properly whilst maintaining balance and impulsion, it must step up under itself, bringing the rear inside hoof forward and towards the midline of the belly, with enough energy. A horse gets that impulsion from the rider's leg, which creates the energy.
So, in reality, to get the best bend with the best balance from your horse, one needs to use all four limbs as well as their weight properly......though in a nutshell, one could say that the inside leg is the most active.
That all being said, most riders and horses are never going to need the type of bend, balance, strength and impulsion needed by upper level dressage horses, and the vast majority of horses only ever need some outside leg behind the girth to keep their haunches in line, with a more passive inside leg at the girth to keep the ribs bent and to be there in case the inside shoulder drops, (with the weight and the upper body position of the rider being correct as well, of course).
You can see, though, how easily it can all become confused.
To avoid that confusion, one needs to always keep in mind that one should apply and adjust EACH INDIVIDUAL AID (BODY PART) AS NEEDED to produce a movement or correct a problem.
If you are going to be trail riding, here is an article with some ideas and tips on specific training for trail riding. One section does give some basic tips on starting neck reining.
Training for Trail Riding
Also, I really prefer being able to have some contact in case something happens, as Murphy's Law predicts, and things go south fast. I always let my horses stretch out, but I don't give them the entire rein in unpredictable places, such as on the trail or at a busy show. Turkeys suck when they flush between your horse's legs, and there may be an umbrella opened on the rail of the warmup arena. 
