A couple pro tips:

Make friends quickly. Make enemies slowly. Be patient and communicative. Don't lose your temper. Never get cocky.

Don't leave yourself open to be backstabbed by a "friend". I have made that mistake many times then someone takes a quick dash for 18 or gains a huge advantage against everyone.

Having played a game with you, I agree with figles.

Your opening diplomacy needs to be improved. I would advise you research a few good opening moves/alliances/etc with countries that will help you start out your game on a good foot and get you going from there.

You also seemed to be a little bit oblivious of when others were going to attack you. For instance, when I moved my armies in Tyrolia and Venice in '01 and took Trieste. Just because I said I was peaceful towards you, you let your guard down and let me into your home centers without a fight.

So a good start would be improving your opening moves and building good diplomacy between other players.

same, you allowed me to kill you by focusing on an easy front before securing me with some real diplomacy, you got too big too quick and i had to kill you, you forgot the biggest rule, CYA, cover your ass!

Diplomacy is the key. If you are more communicative, people will trust you more and want to work with you. The tactics are a result of how well you work with others. you may have the best tactics for just you, but the optimal moves need cooperation from others usually. Keep talking, keep working. Forgive stabs if it is advantageous to you. I trust a guy that is funny and talkative more than a guy that never speaks.

I think speaking should be made mandatory. If you don't speak you go into CD. I get so frustrated if I'm say Germany and France or Austria refuses to talk. They're still there and they play moves but they just don't reply. I mean what is the point?

Here's a nice collection of articles sort by topic and country.

http://www.diplomacy-archive.com/resources/strategy.htm

Seconded for V+'s link. Tons of good info there.

Take it from a moderately tallented old guy who played ftf and mail games probably before you were born, it's called Diplomacy because that's what wins games in the long run. Alliances matter. Honor matters. Interpersonal skills matter. Even the best get stabbed and even the worst players can win, but over time it's about taking care of your allies. Ask the people I've played with, even those I beat, they tell you what I said was true.

@ general: "I think speaking should be made mandatory. If you don't speak you go into CD. I get so frustrated if I'm say Germany and France or Austria refuses to talk. They're still there and they play moves but they just don't reply. I mean what is the point?"

It would be silly to make it 'mandatory' to speak. As a general rule, if someone doesn't respond to your comms, you must assume they are hostile.