Start with a strong foundation
All foundations begin with a footing. Single story houses have a concrete footing which is 6" thick and 12" wide. Two story houses have footings which are 8" thick and 16 inches wide or wider. In earthquake zones like Washington and Oregon there are usually two pieces of #4 (1/2" diameter) rebar suspended in the concrete.
Footings are placed under the frostline and on undisturbed earth.
Vertical sticks of #4 rebar are placed into the wet concrete footing to make a positive connection to the foundation wall. Sometimes a groove or keyway is added to the footing.
Rebar is also placed in the foundation walls. The number of bars and spacing is determined by a number of factors. The purpose of the rebar is to provide tensile strength to the concrete. Over time it will prevent cracking, settling and heaving.
J-bolts are used to anchor sill plates which floor joists can attach to to anchor the building to the foundation. J-bolts get their name from the bend in the bolt which normally fits under a piece of horizontal #4 rebar to prevent uplift.