Play an opening you usually play.
For some reason weaker players play odd opening moves thinking
their better (higher graded) opponent knows all the theory.
They don't.
Don't try and mix it, play solid sensible chess.
Don't touch your pawns. Weaker players destroy their middle game
positions with thoughtless pawn moves.
There is nothing more annoying for a higher rated player than a
weaker player who does not make blunders.
The onus is on the stronger to prove he is the better player.
Develop, castle and leave your pawns alone.
Fight for key central squares and open files.
You lost this one 'cos you refrained from castling on or around
move 8. Your 5.f3 was crap - 5.Nc3. You have moved your d & e-pawns.
No more pawn moves until the Rooks can see each other.
Your opponent developed and caught your uncastled King in the centre.
Bad play by you, you made it easy for him.
Your opponent missed a mate in one on move 13.
[Event "November 2008 Mini Quartets V 1425-1450"]
[Site "http://www.redhotpawn.com"]
[Date "2008.11.28"]
[EndDate "2009.05.12"]
[Round "1"]
[White "Renars"]
[Black "fuzzyamp"]
[WhiteRating "1456"]
[BlackRating "1516"]
[WhiteELO "1456"]
[BlackELO "1516"]
[Result "0-1"]
[GameId "5705147"]
1. e4 e5 2. Ng1f3 Nb8c6 3. d4 exd4 4. Nf3xd4 Ng8f6 5. f3 d5 6. Nd4xc6 bxc6 7. Bf1d3 Bf8d6 8. Nb1c3 O-O 9. f4 Bc8g4 10. Qd1d2 Rf8e8 11. Qd2e3 Bd6b4 12. Qe3f2 dxe4 13. Bd3c4 e3 14. Bc1xe3 Nf6e4 15. Qf2f1 Ne4xc3 16. Bc4xf7 Kg8xf7 17. Qf1c4 Qd8d5 18. Qc4xb4 Re8xe3 19. Ke1f2 Qd5d2 20. Kf2f1 Bg4e2 21. Kf1g1 Be2d3 22. h3 Re3e2