What practices do you consider most essential during software construction?

Code reviews
Continuous integration
Dedicated QA staff
Delivery cycle 2 months or less
Delivery cycle 6 months or less, but greater than 2 months
Delivery cycle greater than 6 months
Developer co-location (non-distributed)
Developer team w. "flat" hierarchy
Developer team w. strong hierarchy (chief programmer model)
Emphasis on 3rd party components / libraries / frameworks
Emphasis on code aesthetics (style guidelines, modularity, DRY, etc.)
Emphasis on functioning code (YAGNI)
Emphasis on internally developed components / libraries / frameworks
Formal project tracking (dependency tracking / scheduling via Gantt / Pert charts or equivalent)
Language choice
Requirements analysis / usability
Scenario / use-case based development
Software cost estimation (e.g., function points, delphi method, planning game)
Unit-testing