The best way to do that would be to keep the League of the Three Emperors intact and find a way to resolve the issues between Russia and AH in the Balkans. If the Germans can find a way to resolve those divisions and keep the League as a united bloc that would very neatly avert WWI. Revanchist France might be spitting mad at the Germans but they aren't stupid enough to pick a fight with Germany, AH, and Russia on their own.