[samdive]

My advice to beginners is to start off your freediving career by spending 2 minutes before each dive doing deep, slow belly breathing and nothing more fancy than that. That is certainly enough for people to find their first "limits" and then you can add in some more advanced techniques/training if or when you need to.

I wouldn't advise anyone to experiment with hyperventilation other than in very controlled situations with a coach who knows that they're doing (and most coaches won't let you anyway!). I've had a few blackouts in my time and I think every single one can be traced back to hyperventilation - unintentional or intentional - it isn't a good idea!