Employee onboarding is a critical make-or-break moment that directly impacts retention, with successful onboarding improving retention rates by as much as 82%. Yet only 12% of employees believe their companies onboard effectively, leaving enormous room for improvement across most organizations. Common pitfalls include mismanaged expectations, lack of clarity, failure to provide necessary supplies, and overlooking the value new hires bring. This guide walks through the most damaging onboarding mistakes and provides actionable, day-by-day strategies to ensure new employees feel welcomed, prepared, and excited to contribute from day one.