If the siege was initiated by the computer, you could be waiting for days. Sometimes they'll even leave and the siege will drop after a week. At the same time, the stupid commanders will wander off if anything comes close making the attack prolonged.
If you start it yourself, you'll have the chance to "Lead the Assault".
You can get villages as fief awards from your King, or you can capture them by taking castles/towns (each have at least one village associated with them).