If you can utilize the element of surprise in a game of chess you are at a great advantage over your opponent and have a winning edge. However, surprising more experienced players with a hidden attack can be tough to do, but may be worth the try. A hidden attack is one which your opponent does not see coming and is unprepared to respond to. Implementing a hidden attack on an opponent's king is particularly effective.
A hidden attack is one where you have a primary piece, such as a rook, that is not threatening your opponent at all. In front of this rook you have one of your knights in the same file. Your opponent may be concerned about where you will be moving that knight, but not concerned about the rook due to its position on the board. This is where you can make your hidden attack. Move your knight so that the rook is now threatening one of your opponent's primary pieces or even your opponent's king. If it appears to your opponent that you are going after, say their queen, your opponent may be focused primarily on that, and not realize that you are actually threatening their king through a hidden attack.
It is important in chess to not telegraph your strategy if at all possible. This means concealing your threatening strategy by way of making it appear that you are simply defending your own pieces. The best defense mechanism against falling victim to hidden attacks is to analyze the entire board and think broadly. If you can see what options your opponent has in he next two or three moves, instead of just the very next move, you can do a good job of defending against hidden attacks.