They are made automatically IF there's a tradehouse in all the connecting provinces. If there's one province between them with no tradehouse, the traderoute is interrupted, and there will be no business. A strong fleet, connecting all the waterways is therefore very recommendable. It also comes in handy later if you want to conquer the islands in the southern part of the map.
Keep away from Rome as long as possible. The Pope's army is easily overthrown, but he keeps reappearing, and biting large chunks out of your occupation forces.
If there are provinces controlled by rebel armies, try sending an emissary. They are easily bribed, and if things go well, you'll not only rule that province one year later, but also you get control over the rebel armies. Good bargain, innit ?
I prefer playing with the English. Not only do they have a good strategic starting position, but when time expires, you'll get the famous longbow archers. In combination with the Royal Knights heavy cavalry, it's an unstoppable army. Your enemies like to stand and wait until you attack, especially on maps where there's only one small bridge to cross a river. If you deploy longgbow archers along the shores, they are sitting ducks, and will be forced to come to you instead of waiting. You can then overrun them with your heavy cavalry.
Peanuts.
