What is the best way to make a jacket potato in the oven? Need some help fast!

I coat the skin with oil and salt before baking, per Alton Brown http://www.foodnetwork.com/recipes/good-eats/the-baked-potato-recipe/index.html for a salty browned skin and fluffy interior.

Rinse with cold water and sprinkle with a little salt.
Dont bother wrapping with foil but skewer with 1 or 2 metal skewers, as they are metal they will heat up in the oven, helping to transfer heat to the middle of the potato.
Depending on the potato size, generaly cook at about 180 degrees C for about 40 mins - 1 hour.