when an opponent (small dude) come toward you, get lower than him,then aim you shoulder at their thigh, then lock their knees together standup halfway(lifting them) finally slam them on either your right or left side of the ground depending on where your head is. when you are chasing after them from behind, just make sure you get close (3 feet) and then DIVE at them legs and lock them together. trust me this will work but if only you learn to ignore the fear of getting injured. for the workout check this site out
The tackle technique is you need to squat low, keep a straight back and hit them with your shoulder. At 6 foot 3 it may be difficult to aim for knee-height, so I suggest you go for the waist or core.
The same way you would tackle the taller people just bend down more is you can learn to tackle some one who is 5 foot you should be good I think that is about the smallest person on my team and I'm only 5 foot 2
basically go cheek to cheek, put your face at their hips and wrap your arms around their knees and just squeeze, if you have their legs wrapped they aren't going anywhere. do squats, lunges, mountain climbs, and lots of running to build leg muscle.
Squat down as much as you possibly can and wrap up! Do a lot of squats and wall sits and keep running
