If you click on the crown icon it shows you a list of your heirs. Only Princes can become Kings, so no queen matildas :(. The heir at the top will become King once your king dies.

"I train troops in France and England, send them to specialist provinces which build armourers, master weaponmakers and valour bonuses, then send them to spain to get their attack bonus. Currently my specialist provinces are upgrading to fortress and my training grounds are preparing for when I reach the high medieval period, in 1205. I am training feudal seargants and archers with a +1 valour bonus from master spear and bow makers, they also get a +3 armour bonus and just recently a +2 attack bonus. So my feudal seargants are the equivalent of men at arms -1 defense and +1 armour, I think."

I have my unit size set to maximum, so cavalry units get 80 cavalrymen, archers and melee infantry get 120 men and spearmen get 200 men, per unit. However this means it takes 2 years to train one unit, so I made this organization so that I retrain a unit per turn in provinces which give armour, valour and attack bonuses.

So instead of trainined a unit in a stat boosting province in 2 turns I retrain a unit per turn in the province. I don't worry about fighting with armoured units in the desert, I just attack quick and once my knights are tired I use the ol' archers and spearmen tactic to kill the rest off through attrition.