Apologies if they are horribly obvious, but my suggestions are as follows:

- Try really hard to ally with the English. Send a princess.
- Crack out the Swabians as soon as possible. They are staunch, and will steamroll anything on foot in Early. Ditto Huscarles (although you might find that they ruin the game for you as they're just too good).
- Resist the temptation to build barques and go straight for Caravels. You'll need their defensive capabilities to protect your trade.
- Keep an eye on any of the Russian factions that have access to the Northern seas. If they spam Boyars, these guys can turn out to be a real problem, especially if they're royal sons.