[Fantomen]

If you plan to participate in multiplayer games, and you should because that´s where the fun is, get used to playing with CBM right from the start. Most MP games are using this mod. What it does is basically minor changes to make more different strategies and units viable, balancing too weak and strong nations a bit and altering a few mechanics that are considered "broken".

A good way to start learning the trade is to play some nations using the strategies outlined in any of the guides in the strategy index.

Don´t hesitate to start a newbie game yourself in the multiplayer forum if there is none recruiting.

Read the manual. Yes seriously, read the manual.