This is interesting, however, I disagree with most everything that his been said. guak appears to be the most on track, I second his advice wholeheartedly.
My advice is to specifically think about the flexibility around stalemate lines. Think about where you are building and where your best momentum will come. There will be certain areas near the stalemate line where your opponent may cross them but be unable to hold them (think things like Austria trying to hold STP or Germany trying to hold BUD or VIE). Ideally, you present those areas as weak so your opponent will send their units to these areas. This will trap them while you go take hold of areas on the stalemate or past it you can hold (MAO for instance, is a great stopper).
Another consideration is tactics, as guak mentioned. If you can use two units to hold off your opponents three even for one turn, this will allow you to be in better shape come the end game. An important consideration that cannot be overlooked is forcing disbands of your opponent. No matter where that disband occurs, they will need to rebuild somewhere further away from critical territories. Lastly, if you can put pressure on the home SCs of your opponent and force them to delay builds due to lack of space, this will help a ton.
I would also recommend sticking to AvF and IvG, in my opinion these are the only two balanced variants. In my opinion, Italy and France may have slight advantages, but the correct application of tactics and strategy can overcome this.
I have played a ton of these 1v1 games, and while I am not exceptional at them, I get by and have a lot of experience with the dynamics. If you are really looking to get better, you might try and pick the brain of Devonian. He is unquestionably the best player in these variants.
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