This is the beginners corner
As you run your scans and find the open ports , you want to see what services are running on the open ports and what version.
Depending on the scan you use it may show you this . But if not you run different scans that will. * nmap scripts also great *
Once you have the service and version you can get your google foo on and more than likely find vulnerabilities.
You can use google , security focus , exploit-db and so on.
You also want to find the OS version as this will also help in your exploitation for exploits and privilege escalation.