There are easy to follow steps clearly outlined on the wiki. It tells how to setup the environment and how to download and build the source.
If you then go to graphicall and create an account, after logging in, there should be an option to upload a new build.
Update: To create an account on Graphicall.org, people now have to go to the IRC channel #blenderstorm on freenode and leave a request for an account (just preferred username + email-address is enough). An admin will create the account when the request is received.