I played since I was 9. Living in the UK.
If I was Dungeon Master I would not split the XP with the NPCs. But like everything in D&D the rules are there to be broken.
So if a player was really just letting the Hardcore NPC Barbarian mash up the place when he was infact also playing a Hardcore Barbarian I would give the player v.little XP. But if the player was a mage, and relied on the NPC barbarians strength and rage then I would not be so harsh on players character.
If you are playing a 6 hour small adventure. Then I advise no XP to NPCs
But if you are playing a campaign (which is like several small adventures tied together) then if you have a major NPC figure you may want to give him XP, so the players can see how HE is advancing also.
There is great resources on
http://community.wizards.com/
If you are playing D&D red box, then you will be starting in Forgotten Realms. Eberron is the most current land available to play in. Msg me and I'll give you details of where to purchase epub books for v.cheap.