This is a great game and there is lots of advice out there. I still have a lot to learn myself with only 106 games but I did not find the advice I was looking for so here is a short list of things that I did so far to get me to Colonel
1) Know your tactics - the key here is thinking through what is the most likely response from the opponent? Don't just be rationale about it, think about the opponent and think what type of player are they? I check out their ratings and see if they are rated more for balanced behavior or reckless.
2) Know what type of game works best for you. For me, my style favors the following game: Standard (not freestyle), no fog, reinforcements chained or unlimited, flat rate, automatic deployment, and 4-5 players. For me this also is generally the game that minimizes luck as a dominant factor. Sure escalation and freestyle take a lot of skill but the timing and the requirements to stay online are troublesome for most. Also, luck can be a determinant with escalation since its too much up to the cards - did you wipe the other guy out to get cards? Did you get a set in 3 etc etc.
3) Know the Map - super well. Which way do the attack flows go? D day favors the ships and the 3rd crusades favor the european power positions for example. Also, the edges are almost always better than the middle - civil war strongly favors Texas/Northeast and ww2 Europe favors Russia or France/UK. Know the details as well - the Napoleon map connects Italy with Switzerland, for example. Getting control of choke points is key as well. Therefore, in Napoleon if you have France and Spain, adding Italy actually decreases the number of choke points. In Classic, its why Oceania is favored with its single choke point. Continue your attacks to drive to the next best choke point.
4) Timing is Key - when do you deploy your cards? When do you decide to put up a truce or end one? When do you move from a defensive to an offensive stance? If you stay static (stick with the same style) I think its not a good approach at all since the game conditions change and therefore your response needs to as well.
5) Troop preservation and increase is more important as a focus in general than keeping and breaking bonuses. So the practical applications of this strategy?
A) Don't go on these silly excursions (golden chef special) where you break multiple people's bonuses and don't further your own strategic position. It may feel good breaking bonuses but you've also lost your army in the process with nothing to show for it. B) Do let the guy who is intent on breaking your x bonus break the bonus if you can not prevent him from doing it. In other words, if he has a 7 stack and you can only defend it with at most a 4 stack then just defend it with 1, if you know he wants to break your bonus. Keep the troops off the bonus edges until you can move in enough troops to silence his aggressive stance.
C) Keep the important borders quiet of activity. Brazil/Africa or Baden/Burgendy - make sure that you are not continually warring with another party over a border like this. If your opponent wont let you keep it and you cant knock him out, then just withdraw. Don't fight multiple times over this - it will bring both of you down relative to the others.
6) Diplomacy - you've got a chat box out there - use it! My only rant is people who get mad for "giving directions" or saying x. OF COURSE! Its a game and highlighting what is a good win-win for both sides is part of the game. The other player wont do what you say unless its to his advantage as well. If you want a silent game, then play chess or some other game. Try your best to keep your agreements - and make them specific. Say ONLY a truce between X and Y or it ends in 2 turns etc.
7) Know your Strategic Options - I list out a few options that people should consider at any point in a game. In all of the options below, you should be preserving troop strength, achieve the right positioning in the map, and maintaining your diplomacy. Note that the strategy may change in the course of a game - it always depends on the situation and how diplomacy is going as well. The following are all for multiple player games. Strategy for 1-1? Get good luck

Options:
A) The Alpha Male - Get out in an early lead, follow that lead and aggressively counterattack anyone that threatens you. Be extra nice to people who are playing along as well.
B) The Sidekick - you know that going against the Alpha male is going to get you knocked out. The others are not playing nice against Alpha Male so you offer friendship. The key here is knowing when to go your own way AND knowing that there may be a time when Alpha Male will get so weak (because he is the focus of attacks) that you may have your day in the sun.
C) The Suicide Bomber - its not a strategy I like but it is an option of last resort that you should consider. Stack all of your forces on a single territory, keep edge strength to 1 and then announce a full counterattack if someone attacks you. (picture all the forces on Lima/Peru instead of Brazil/Venezula on Classic) Often you can not win, but you can determine who wins. This knowledge and using it through diplomacy can get you to a point where you may be able to recover
D) Sherman's Marching Army - sometimes you have the troop strength (its the key) but not the map position. You are caught in the middle between two players etc etc. Put all of your troops on one territory and MARCH! get to a new position in the map where you can defend and restart over.
E) Alcatraz - you sit on a piece of territory nobody wants and just build up strength. You let others war it out over the bonuses and focus only on your troop strength. I don't personally like this strategy (is a bit cowardly and passive for me) HOWEVER, in certain maps like Feudal - I think its a valid strategy and one that works given the bonus structure.
Options that do not work:
A) The Terminator - this guy goes around and hits the guy's bonuses who just got to a slight lead. This can be great as a tactic but as a strategy it just ends up weakening yourself. Don't focus on breaking bonuses - focus on building up your position. Borders where the wars don't stop will kill you. Playing on the border of a terminator is tough. Honestly, I think that the only way is to eliminate them or do a Sherman's move. The Alpha male is not as focused on the opponent bonuses but more on their strategic position and their troop levels
B) Mr Revenge - counterattack if it builds your position or if you think it will change the behavior going forward of your opponent. Don't do so out of pure vengeance. However, I will admit that I have been Mr Revenge in a couple of games - sometimes it IS about making the guy you don't like lose - even if you lose more points. This IS a game after all and we are human beings!

I would welcome advanced advice as well - please chime in with your own recommendations!
Ted (I'm not French btw)