We found this container at Fire Pit Art http://www.firepitart.com/ . They have a wide selection of steel containers. We chose this one " Saturn" because it is simple and raised off the ground.Raised is good, better than ground level or in the ground.
If you are doing this on the cheap use a tractor trailer rim on top of a pickup truck rim.
Pits can be fire by either gas or wood. We prefer wood.
The fire pit should be placed in a defined area. We used 1/2" river gravel to insure fire would escape. Seating should be movable, smoke and heat. A chair is more comfortable than logs.
A garden can be added around the outside of the wall , vegy or flowers.
And remember to follow Smoky the bears advice about fires.