On your fifth stop, eight get off and seven get on. It is the author's job to give the reader the clues that point to the answer, then muck it up by throwing in clues that have nothing to do with the answer at all . . . That's what just happened in the above puzzle. I gave you all the facts, and told you everything you needed to know. I don't know the answer, because I don't know the color of your eyes, but if you were sitting there adding and subtracting passengers only to be asked a question which seemingly has no relevance, then I was successful in planting the clue and distracting you with the red herrings.
Clues are the facts that lead to the truth.
Red herrings are fish that stink really bad and draw a lot of attention but don't mean anything because they don't actually exist. In other words, they are false clues. Let's start with planting clues. Well, maybe it is a little complicated, but no worse than, say, devising a plot or creating an interesting character. There are two ways to approach planting clues.