Okay.. well first off you aint going to get anywhere with what your doing.. or at least you shouldn't unless the system admin has fallen asleep during the entire build of his server.
First off the bat.. what i would suggest is getting some sort of port scanner .. nmap will do JUST fine.. do a google on it.. have a read of the documentation available on it so you know exactly what it does.
Then run a scan on the IP address you are "testing" to attempt to reveal any open ports available.. from their you will have an understanding of what services are open to you and where you can start looking. See what is running on each port..
My experience sits with web application security .. so what you could also do is check to see if their is any HTTP or SQL ports open .. you might find it could be a lot easier going through an incorrectly configured web service..
Knowing what technologies are being used is going to be key.. is it a unix machine with apache server .. so you can start looking at that ..
or is it Windows with IIS running .. in which case the possibilities are endless
One thing on windows machines i have found VERY common on testing is the permissions ... some admins get very sloppy with how they assign permissions.. haha
Anyway .. you have a lot to start digging around at.. take your time.. you aint going to do this in 5 minutes ...