My friend and I were somewhat experienced players, or at least had played before, and were teaching our friends how to play. I drew Germany, and my buddy drew France. Not particularly wanting to fight against him when there were easier targets around, we agreed to a non-aggression pact.
After taking Holland and Denmark, I sent most of my armies toward Austria, but was having difficulties with a particularly stubborn/stupid England player that kept trying to convoy his army to Denmark. Turn after turn, it was the same thing: him convoying his army and mine staying there. I was working with Russia, so he didn't have any help from the other side.
France still found a way to get at me though. He talked Russia into supporting the convoy, then moved himself into London, and shortly thereafter took the rest of England. I got Denmark back, but that was nothing compared to the 3 SC's France stole from England.
Anyhow, that was the original reason I didn't want to fight against him--he was good. I don't remember what happened after that, but it probably involved France getting a lot more centers than Germany. Anyhow, it was the slickest thing I had ever seen, and all revolved around one territory--Denmark. The good players will even get you without moving a single army against you.
Jason
I thought that I'd comment on Both the province of Ruhr and the Province of Denmark at the same time, as they are two sides to the same coin.
On one side is France, and on the other side is England.
I have found it quite true that an army in Ruhr for Germany is only stoppable (in the long run) by an army in Burgundy for France. If Germany can convince the French to trust them, a move from Munich to Ruhr to Belgium can win in Europe for them, as a new army can be built in spring 02 in Munich, and if the French have attempted to take any builds (you can support a move into belgium with an already existing fleet in Holland, so he probably won't get that one), then they will scramble away from them in the Fall 01 turn when they realize they're under attack, normally leaving them without a good defense against a crushing 5 unit army.
If in 01 you can take Denmark,with the Berlin fleet, Holland using your two armies, then even a mighty English fleet will have a hard time doing much, especially considering that you can build another fleet in Berlin and your two armies around the Holland coast will prevent any landings.
When I have gone with this strategy, England is most often forced into convoying armies into Scandinavia, which are then normally lost because they cannot defend them from the Russians, and keep a convoying navy in the North sea at the same time.