What are my options for an unplayable ball?

You alone decide whether your ball is unplayable, and you can do it anywhere on the course except in a penalty area (Rule 19.1). In the general area or on the putting green, add one penalty stroke and choose (Rule 19.2):

1. Stroke and distance: play again from where your previous stroke was made. You can do this even if you haven't found the ball.
2. Back-on-the-line: drop behind the ball's spot, keeping that spot between the hole and where you drop, as far back as you like. The ball must come to rest within one club-length of where it first touched the ground, not nearer the hole.
3. Lateral relief: drop within two club-lengths of the ball's spot, not nearer the hole. If the ball is up in a tree, measure from the spot on the ground directly below it.

Options 2 and 3 require you to know where the original ball is.

How to drop (Rule 14.3b): let go of the ball from knee height (your knee when standing), straight down, without throwing, spinning or rolling it, and without it touching you or your equipment before it lands. Bunkers have extra rules (Rule 19.3).