There's so much to learn about chess I'm not going to go through the whole game, but here are a few basic tips:
i. Fork: The most basic capture move, put a piece in a position to attack two of your opponent's pieces. He will have to move one, then you take the other.
ii. Pin: Using a rook, bishop, or queen, put yourself in a position where you are threatening a piece with a more valuable piece behind it. The piece will be "pinned" in place because if it moves, you will take the valuable piece.
iii. Skewer: Similar to pin except that you threaten a valuable piece with a weaker piece behind it. The valuable piece (e.g. King or Queen) will have to move and you can capture the piece behind it.
iv. Opening: Opening is the most crucial point of the game. The best strategy is to move your two center pawns forward two spaces, and then move the knights towards the center as backup. Some players even move the bishops out into the center, but it can be difficult to complete the entire strategy without your opponent attacking and forcing you to defend yourself.
And you say you've heard taking the middle is good, this is true. Take the middle as stated above with knights, bishops, and pawns. Never attempt to hold the middle with rooks and queens because they will either be taken or forced to remain in one place to protect other pieces. The queen should be able to move independently around the entire board, and the rooks are mostly backup pieces.
Castle with your King whenever possible.