The method is the following: Leave a nail in bleach 24h in order for it to rust. Drive it through the stem right near the bottom, few days before harvesting time.
The logic: The plant will realize that it's dieing and will secrete a protective hormone that accelerates bud production, not cannabinoid production. You'll end up with more buds, not with a higher THC concentration.
I did not try this, so I have no idea if it does work, but I have read some posts around here from a guy who says that it does have a big impact in the buds...