for the first - not always. for example, if someone makes a sexist/racist remark, i may not know *what* to say, but I will respond in some way (otherwise it may appear as if i agree with the remark), such as "that's not cool" or "please don't talk like that in front of me".
the second -probably not.
if you are referring to your other thread on entering the workplace, then: no. if you are new to a job and you don't know what to do, then you speak up. or if you are new to a college, a house of worship, a volunteer job, first time you are flying somewhere - then ask. there is nothing wrong with asking. when you do "nothing" you are actually making a choice, you are doing "something", it just happens to be that the "thing" you are doing is refraining from action (I hope this makes sense). and like with your first "rule" - sometimes keeping silent or doing nothing is "doing something".