In golf how many strokes are you penalised for a lost ball?

If your ball is lost outside of a water hazard the penalty is stroke and distance. Return to the place that you last played from, drop (or tee, if it was a tee shot) and play from there. Count the shot that led to the lost ball and add one more, and count the replay.

Many beer leagues play drop it somewhere in the neighborhood of where the ball probably ended up, add a penalty stroke, and play on. Not USGA sanctioned, but on a public course where you have to get done before sunset it's a good way to keep the game moving.