Get the original sources (normally) as a compressed tarball (foo.tar.gz or foo.tar.Z) and copy it into DISTDIR. Always use mainstream sources when and where you can.
If you cannot find a FTP/http site that is well-connected to the net, or can only find sites that have irritatingly non-standard formats, you might want to put a copy on a reliable FTP or http server that you control (e.g., your home page). Make sure you set MASTER_SITES to reflect your choice.
If you cannot find somewhere convenient and reliable to put the distfile we can ``house'' it ourselves on ftp.FreeBSD.org. The distfile must be placed into ~/public_distfiles/ of someone's freefall account. Ask the person who commits your port to do this. This person will also set MASTER_SITES to MASTER_SITE_LOCAL and MASTER_SITE_SUBDIR to their freefall username.
If your port's distfile changes all the time for no good reason, consider putting the distfile in your home page and listing it as the first MASTER_SITES. This will prevent users from getting ``checksum mismatch'' errors, and also reduce the workload of maintainers of our FTP site. Also, if there is only one master site for the port, it is recommended that you house a backup at your site and list it as the second MASTER_SITES.
If your port requires some additional `patches' that are available on the Internet, fetch them too and put them in DISTDIR. Do not worry if they come from a site other than where you got the main source tarball, we have a way to handle these situations (see the description of PATCHFILES below).