• If you are instructed to attempt a check, you must do so, although you may choose to fail; if you do, your result is 0.

• If you are instructed to succeed at a check to do a thing, and the instruction does not use the word "may," you must attempt the check; if you succeed, you must do that thing.

• If you are instructed to succeed at a check or do a thing, you must attempt the check; if you fail, you must do that thing.

• If you are instructed to either attempt a check or do something else, choose one of those options.

• If you are presented with two or more options, none of which require a check, you may choose any of those options.

You may not choose an impossible option unless you have no other choice.