Poor employee onboarding can cost companies significantly, with negative experiences being twice as likely to cause new hires to seek other opportunities. Only 12% of employees believe their companies onboard well, yet successful onboarding can improve retention by 82%. This guide identifies common onboarding mistakes like mismanaged expectations, lack of clarity, insufficient supplies, and failure to recognize fresh perspectives. It then provides actionable strategies for creating a positive onboarding experience that starts before day one and continues through the first ten days.