Foundation work depends entirely on what's underneath it, which is why the site preparation phase matters as much as the foundation itself.
The general sequence
Before foundation work starts, the building area typically needs to be cleared of vegetation and any existing structures or debris, excavated or filled to the correct elevation, and graded to the target surface. Fill material, if used, needs to be compacted properly — often in specified lifts — to provide stable support.
Utility trenching for water, sewer, electrical or other services often happens around this phase as well, before the foundation is poured over them.
Why this is worth getting right
A foundation is only as good as what it's sitting on. Skipping proper compaction, ignoring drainage, or rushing the grading phase to save time or money tends to show up later as foundation problems that are far more expensive to fix than the site prep would have cost to do correctly.
This is general information, not engineering guidance for your specific project — always follow your engineer's or builder's specifications where they apply.