In addition, build a fleet and be ready for the horde. Treb is great for the archers (+1 for the prov. +2 with master bowyer); dedicate a province to V. Gaurd production and build as many as you can as long as you can; some let Naples go but some use it as a stepping stone for Sicily...never been that lucky myself HA are great! but the Moslems usually have better; Bulgaria/Greece (or Serbia) make a nice buffer for Constantinople.

Egypt gives a southern choke point; Georgia in the east...once you have this you pretty much know where any invader has to come if you have a strong fleet. Crusades I hate'em and once I'm established i just kill'em all

can't think of much more atm Enjoy!