Fifteen minutes a day, reward-based throughout, adapted to your breed — with honest limits about what needs a professional in the room rather than a plan on a screen.
The dog knows 'sit' in the kitchen and nothing at the park — because practising in a quiet room isn't the same as learning.
Dominance theory, alpha rolls, shock collars. The field moved on from all of it; the internet didn't, and the old methods actively make some dogs worse.
A good one is worth it, especially for serious problems. For everyday obedience, most of what they teach is a structure you can follow yourself.
A collie bred to take direction and a hound bred to follow scent independently need different approaches — and different expectations about off-lead reliability.