Do use the macros provided in bsd.port.mk to ensure correct modes and ownership of files in your own *-install targets.
INSTALL_PROGRAM is a command to install binary executables.
INSTALL_SCRIPT is a command to install executable scripts.
INSTALL_DATA is a command to install sharable data.
INSTALL_MAN is a command to install manpages and other documentation (it does not compress anything).
These are basically the install command with all the appropriate flags. See below for an example on how to use them.