Best idle practices?

I'd like to know how long to idle my truck when starting and stopping.

Should I warm up to full operating temperature (130°f) before moving the truck at all, or just on trips?

Should I wait for it to drop to that temp before turning off the engine too?

I've been told a lot of things from a couple people who seem to be at odds about all this warm up/cool down nonsense.

 

So its fine to just go?

When I wait to warm it up, my oil pressure flucuates until it hits temp. I didn't know if that was normal, so figured I should just wait it out.

 

As far as oil goes, in trying to change it every 15,000. I kind of freaked out when my dipstick was a gallon low after being fine for a couple weeks. My mechanic told me its normal when I'm due for service.

If only it were just the oil that needed changing though.....

I'm playing clean up after the previous driver. Two dead batteries and the starter died on the floor of the shop.