Shenetworks Recommends: Using Nmap Like a Pro 

Executive Summary: This article is an introductory guide to Nmap, explaining common scan types (-sL, -sV, -Pn, -p-, -T4), output options (e.g., -oX), the script scan mode (-sC), and a selection of useful NSE scripts (sshv1, dhcp-discover, ftp-anon, ftp-brute, http-enum, http-passwd, http-methods, ms-sql-info, mysql-enum, NFS-showmount, rdp-enum-encryption, smb-enum-shares, tftp-enum). It is aimed at helping network engineers and penetration testers discover hosts, services, and potential weaknesses rather than reporting an incident.