Hi munari, welcome here, looking forward to playing you sometime.
Most importantly, talk a lot to people. If you are quiet they expect you to be an enemy. Talk with everyone, even Turkey and England have a lot to discuss.
Second, talk a lot to pleople.
Third, balance trust and paranoia. You will be stabbed and you will stab yourself.
Fourth, learn the rules, read an official (boardgame) ruleset, not the one on the site here. Know what supports and convoys can achieve, know about self-standoffs, supporting opponents, cutting support, dislodging units, when attacks and convoys fail and succeed...
Fifth, sort of "etiquette" rules. Don't abandon games, play them out, no matter how bad they go, don't insult people, don't miss turns that usually effects other people as well, not just you, If you know you will have trouble getting your orders in, try arranging a pause (almost every good player will agree to a pause when given a reason) or get an account sitter.
Sixth, never give up. You can be included in a draw with one unit left, in rare cases even without a SC.
Seventh, do not play to maximize your points, even if it is tempting in the beginning. Play for a win, always. If not possible play for a draw. If not possible try to get existing alliances to break to turn th esituation. Then nothing for a long time... If nothing of hte above is possible play for a survive. If not possible eiher, ask yourself what went wrong.
Last, always trust me.
Have fun on the site and learning the game! Arguably the best game ever :)