Read Server Documentation Part One
Read Server Documentation Part Two
Third video linked below.
There are three stages to the actual server build. First, you look at your Network Documentation Binder (NDB). That should give you all the information you need to fit your server into the network (IP address, who serves up DNS, DHCP, etc.) What's the name of the machine and domain?
A nice network map with key information is helpful.
The second thing you need is a TSR (troubleshooting and repair) log. This is a great tool for tracing your steps. Whenever you need to make a decision or enter something on the server, write it in the log!!! See http://blog.smallbizthoughts.com/2011/07/sop-friday-troubleshooting-and-repair.html for more information.
There's no point in keeping things like administrative passwords, ILO username/pw, etc. on little slips of paper. Put it on a TSR Log and then copy it to the machine spec sheet.
The third thing you need is the actual Machine Spec Sheet. This is a super simple form that just contains the most critical info you're going to need. What's the name of the server, the IP address of the server, the support tag or serial number of the server, etc.?