Usually my way of doing is I accept all candidates for interview sessions. Then only will review and choose potential candidates. Maybe 2 to 3 candidates like that. Before I go for background check, I will inform boss or department manager who requested for hiring, at last background check then decide.

Background check must do it in a polite manner.

Background checking is by calling up the previous company to query how his attendance, job performance. If you want to confirm his previous salary like what candidate said, then ask to bring past 1mth salary voucher or payslip together with resume, certs, etc