Ask what lies below the slab
Existing fill, disturbed ground and unsuitable material can affect the work. An assessment should explain the proposed excavation and support preparation. Do not assume that every site needs the same amount of imported material or the same preparation method.
Make preparation visible in the quote
Look for a description of removal limits, grading, base material where specified and compaction. Ask how unexpected soft or unsuitable areas will be handled and approved. A low concrete-only price may exclude necessary preparation.
Coordinate water and utilities
Water movement and previous utility trenches can complicate support conditions. Discuss drainage concerns and have relevant underground services identified before excavation. Any rough-ins should be coordinated before the base is finalized.
Review before placement
The stage before the pour is the time to confirm elevations, forms, specified reinforcement and embedded items. If inspections are required, schedule them in the sequence. Once concrete is placed, hidden preparation is much harder to evaluate or change.