I don't think there is an absolute definition of this concept - it is different for each individual, and there is nothing I believe in more strongly than I do in individuality. However, my personal definition, as nearly as it can be expressed in words, follows:

If an action causes much more good than harm,
or
if the sole harm is to the person taking the action, and such harm is either reversible, or something on which that person's view is unlikely to change with time,
or
the action is the optimum way to prevent greater harm to life (with preference for human life) as a whole,
the action is right.

Otherwise, it is wrong, and an ethical person will not act in that way and will indeed try to prevent others from doing so.

I've thought about that definition for literally years, and think it covers all the bases. Please, however, as always, /msg me with any comments.