When playing a higher rated player such as a grandmaster, play whatever opening you have the most knowledge in. It does not matter if it is a Caro Khan. or the Center Counter with 1. e4  d5  2. exd5  Qxd5 or the Goring Gambit two pawn sacrifice with 1. e4  e5  2. Nf3 Nc6  3. d4  exd4  4. c3  dxc3 4. Bc4 cxb2 5. Bxb2.

Also, if the higher rated player offers a draw and if the position is not already a pretty dead draw, do not accept but instead try to figure out why the higher rated player believes he has the worse game or a lost game.

Or he believes it's a draw :D

Oh, I think I see what they're saying now.

Basically the advice is that passive play is bad no matter who your opponent is, but it's especially deadly against a much higher rated player.  So it may be tempting to curl up in a ball and play for a draw, but it's a sure way to lose.

If that's the advice, then I agree

Yes, for sure when you are playing a higher rated player, do not play for a draw as playing for a draw will invariably keep you from finding some very good moves!

Also, don't think of your opponent as some omnipotent.  When I was younger I did this with 1200s (INTERNET 1200s no less!) thinking they were untouchable. 

Your opponent is higher rated for a reason, maybe it isn't a typical reason such as you've been out of chess for awhile but studied like crazy so your skillset is actually hundreds above your rating but it's usually because he's better than you.  The best thing you can do like I said above is not overestimate your opponent. 

No, if it means "where you know the most book moves".

Whatever opening you know the most moves, he knows more than you. (except maybe for real crap that he will refute on the board)

You need to be able to find a plan at any deviation from your book, and that is the only valid opening-choosing strategy, even if it means knowing only up to ten moves. If you know 30 moves of the Ruy Lopez and he suddenly deviates from what you thought he would play on move 15, you will die in the maze if you don't know what to do.

Isn't that how it is on every level?  Tactics only make sense either in the form of a positional or material gain.  If a fork and mate threats lead to a better endgame due to the opponent having to make concessions for defense then that's what one does. 

That's an interesting question. I think up to 2000 (roughly), blunders and tactics are by far the most relevant factor, as most players will err positionally.

Above this bar, you'll find a mix of strong tacticians and more balanced players.

Above 2200, people are pretty good positionally (at least from by window, maybe not for a GM).

So it's difficult to outplay someone positionally, if you're not a strong positional player to start with : won't happen that much under 2000-2100 I think.