Here's a very short game I played against a 1600 player (who was as high as 1775). I'm often surprised how weak some of these 1600-1700 players are. Well, here's the game:
1. e4 d5
The Scandinavian Defence, which I've found to be particularly effective at the lower levels.
Simple and best. I've seen 2. e5 quite a few times, but after 2. ... c5 black gets a favorable Caro-Kann-like structure without losing a tempo for c5.
2. ... Qxd5
My personal favorite. The other major alternative is Nf6. But I'm not too fond of this knight sortie. After 3. c4 c6 4. d4 [4. dxc6 is dubious as it speeds up black's development and leaves white with structural problems for the extra pawn] cxd5 play transposes to a Panov Attack, and 3. ... e6 (the Icelandic Gambit) is not my cup of tea.
Natural, winning a tempo. Because of this loss of tempo the whole line with Qxd5 was considered somewhat dubious.
However, Nc3 blocks the c-pawn preventing white from setting up a strong center and it isn't clear if the loss of tempo is a big deal for black. Basically, black is giving up a tempo to prevent white from building a big center.
The modern view is that maybe white should delay Nc3 and play Nf3 or d4.
3. ... Qa5
The "old" main line. Until now I've been playing the "modern" Qd6 with good results, but here I decide to give the old line a try.
White's main move here. White grabs the e5 square and opens the diagonal for his dark-squared bishop.
4. ... Nf6
The most popular choice. An alternative is to refrain from developing the knight to f6, which in certain lines prevents white from breaking up black's kingside pawns with a quick Ne4-Nxf6 idea.
Breaking the pin on the knight and x-raying black's queen. However, the main move here is Nf3.
And for those interested in a little chess history, Bd2 is the move played by Karpov against Larsen at the 1979 Montreal tournament. Karpov lost, but not because of the opening. He overpressed in the middlegame and Larsen struck back. Ah, the pressure of being World Champion!
5. ... Bg4
Recommended by theory. Black develops a piece with tempo. Active piece play is what I love, so I won't argue with theory.
Also, the move played by Larsen.
A strange move, shutting in the bishop. White's best tries are Nf3, Be2 and f3. The text move isn't horrible but slightly passive and possibly the beginning of white's future problems. Karpov played the solid Be2.
6. ... Nc6
Bringing out another piece, putting pressure on d4 and preparing queenside castling. Textbook opening play.
Again a somewhat passive move. It does break the pin on the f3 knight, but the queen is passively placed and loses touch with the d4 pawn. Better was f3.
7. ... O-O-O
Brings the rook into play while increasing the pressure on d4 and getting the king out of the center. Simple and effective.
A pseudo-active move from white. It attacks the black queen but does nothing to address white's lagging kingside development and king in the center.
8. ... Qd5
Aesthetically pleasing and strong - centralizing the queen, piling up on d4 and putting the question to the knight.
9. Nxf6 exf6
White wastes more time while black gets ready to get the bishop into play and connect the rooks.
A pseudo-defence of d4 which falls flat on its face.
10. ... Bxe2
Simple - after 11. Bxe2 there follows Qxg2 and white's kingside is in ruins.
White refuses to give up the g2 pawn, but placing the king in the center given black's activity is next to suicidal.
12. c4 Qe4 13. f3 is met by Bb4+!
11. ... Nxd4+
Horrible. By taking back on d4 white opens the e-file and his king is a sitting duck awaiting execution.
12. ... Qxd4
This should have been played a move earlier, giving white some hope of salvation.
If 13. Qe3 then 13. ... Qd5 14. Qxa7 and Re8+ wins.
13. ... Bc5
Black's activity is overwhelming now. White must give up the queen to save his king and so he resigns.