ACtually kind of rare to see text book form 1-1 open field tackling during games, it's just not a situation that presents often. In my opinion, tackling is the thing about football that is the most talent and natural ability thing on the field. You just cant' really teach angles, leverage, you can just go out do it. The best tackler I ever saw was a kid that grew up on a farm in northwest CT that I played with. He said it was because all he did as a kid was bail hay, and run down the animals and tackle them and pin them down when it was time to sheer the sheep, or whatever they do on farms. I don't know. All I know is he was slow as hell in a straight line, but on the field in the SS position, he could run down anything he could keep in front of him and get in on the ground. That said -
You teach tackling form and do tackling drills for one reason only, player safety. The vast majority of catastrophic injuries in football happen when a player has their head down, eyes down, facemask horizontal, or chin tucked toward the chest and gets contact to the top of the head. Lots of different ways to do it, but the fundamnetals have already been discussed. Head and neck position is the most important thing in teaching tackling. Doesn't really matter what specific drills you're doing as long as you're teaching the kids to keep their grills vertical, up, and eyes on the chest numbers and keep their heads back and shoulders/neck back.
tackling itself, i've taught at the youth level simply as chest to chest contact arms wide open, you make chest to chest contact then wrap up the arms and just keep running through. Don't use the arms until you've got solid body contact with the trunk. I personally, do not like putting young kids in full gear. I think that helmets and shoulder pads shouldn't go on until high school age, but I"m in the minority in CT there. I think there's no easier way to teach kids safe contact, than when they're wearing nothing but a sweater, and pants, but that's my opinion.
When they get older, you start getting into footwork, body position, angles, getting your head and shoulders across the numbers, at different angles and haivng hte proper leg drive and all stuff like that. But the fundamental never changes. Head up.
When you see players lowering their shoulders to drop the shoulder pad into a thigh, or take out the legs or simply lay the shoulder into the chest instead of chest/chest wrap up contact, throwing the body at the legs, and trying to upend players, stuff like that, it's actually just blocking techniques that's being used by a defender, and that's why you see offensive players stay up a lot more than when somebody actually makes body contact and wraps.
A lot of time in the open field, it might not look like a good tackle, but you'll see a defender flying in and laying out, wrapping up, but slide down the player like a ring on a post or something, and end up with the arms wrapped around the ankles, and lying on the ground, and the offensive player is still standing, but has leg shackles on, and then the next defender can bring them down.
As for special teams tackling, it's 100,000% about desire, energy and staying in your assigned space on the field, and shedding your block and then making contact with the ball carrier if he's in your space and putting them on the ground.
We've jsut been very, veyr inconsistent with energy on special teams this year.
The best tackler we've had in this program, IMO, in the past 14 years is Tyvon Branch, and it's why he's a regular SS in the NFL.