Unpack a copy of the tarball in a private directory and make whatever changes are necessary to get the port to compile properly under the current version of FreeBSD. Keep careful track of steps, as they will be needed to automate the process shortly. Everything, including the deletion, addition, or modification of files has to be doable using an automated script or patch file when the port is finished.

If the port requires significant user interaction/customization to compile or install, take a look at one of Larry Wall's classic Configure scripts and perhaps do something similar. The goal of the new ports collection is to make each port as “plug-and-play” as possible for the end-user while using a minimum of disk space.