Not really much of a guide just a few things I've picked up as I've been playing that I couldn't find any information on so I thought I would pass it on with a bit of basic strategy to get people started.

Port forwarding for multiplayer:
You don't need hamachi! I was able to get it working by setting up port forwarding on tcp/udp ports 9100-9105. I think its only using two of the ports but i didn't feel like investigating further as this worked for me and i disable the rule when I'm not using it.

Editor:
In the same directory as the games executable is the campaign editor(ed.exe). This will allow you to create custom campaigns and make any changes to gameplay that you require. You can change anything for any Nation, change the start and end dates of the campaigns and also set any nation to playable in the multiplayer campaigns. I would not overwrite any of the default campaigns so always change the name when saving so you can use the default campaigns as a baseline for any future custom campaigns you would like to make.

I haven't played that much but this is the basic strategy I have been using.

Basic Strategy:
First turn
First thing I do is goto infrastructure and set all my resources to maximize and start upgrading agriculture and infrastructure, I do fortifications as well if possible but usually its a little to expensive to upgrade at the same time. I then check my military and dismiss any unecessary units as they require production of arms and will slow you down as you are trying to build up production/infrastructure/research as fast as possible. I then check my resource usage and make any trade agreements as necessary to make sure I don't run out of resources while I'm getting everything rolling. At this point just try not to let any resources go into the red as once infrastructure is done you will have more money to focus on stockpiling. Then I check my production and usually try to get all my cities to Heavy Industry(10 units) and then after that I will take my larger cities and ports to advanced(50 units) as they require less resouces and can build more advance units once the research is unlocked. It's all about balance try to upgrade production as many as possible at a time but make sure you keep your arms and goods levels from getting to low.

Building up
While you are building production up be sure to keep an eye on your resources and once your infrastructure is fully upgraded I look to the world market to start stockpiling resources. Once you are happy with production/infrastructure/trade I will start to research. I usually start with 200-400 units in research and focus on Land units and tactics. Once I feel like I have a good advantage with my units I will change research to recruiting and build up a big doom stack with a ton of advanced infantry, and the best tanks and artillery I can muster. When my army is ready I will go back to research and focus on whatever I feel will help the most going forward. As my army conquers i leave 2-3 infantry at each location to defend as I conquer with my doom stack. Once you take a region build it up the same as you did at the start however if the government type is different you may suffer production penalties to industry so I try not build any advanced cities away from my starting country unless absolutely necessary.(sometimes you need a fleet on a different front) If the government was different before you conquered it you will only get 37 units instead of 50 from each advanced city.

Remember when building units or upgrading production always keep an eye on your resources, if possible try not to rely on trade to heavily. I generally try to get to a point where I'm only using trade for stockpiling resources as trade always seems to dry up and if you rely to heavily on it you're going to have a bad time.

Hope that helps not much of a guide but its more than I could find with the information out there.