Avoid having to remember the version number (-x) :
pkg_info -xc emacs
Reading Post-Installation Messages (-D):
pkg_info -xD qterm
list the files (-L)
Checking the Disk Space Your Ports Use (-s)
Updating portsdb: portsdb -u
Use portupgrade to upgrade ports or packages:
portupgrade -arR -PP
The -R will check the build dependencies and the -r will check the applications that depend upon the port being upgraded. This will prevent your system from having outdated dependencies and software incompatibilities. -PP means use packages only.
pkg_which is the counterpart of apt-file.