Non-lethal attacks are half damage. Once you bring a foe to 0 hits that way they are subdued.
If you roll a critical hit, it changes the non-lethal back into lethal damage. Attacking is inherently dangerous.
Some attacks (one example lightning) cannot be made non-lethal. For your attacks check with the GM. Only blunt weapon sneak attacks can be made non-lethal.
Non-lethal archery involves load-minor activity of snapping off the points. This does not work for magical missiles as it would ruin the magic.