You might want to automate the process a bit, by using templates. I use the two following templates:

Pkgfile and Pkgfile-git. The second one is for git based ports. The guidelines specify that git based ports should use a commit number, so the Pkgfile will pull all changes, and checkout the specified commit.
If you're interrested, you can take a look at those two scripts of mine: prtmk - prtup.
prtmk will use the above templates to generate a Pkgfile for your package using prompts. The special version "git" will use the -git template, and prompt for a commit number.
prtup is made to update git ports and should be ran in the same directory as the Pkgfile. It will source it, clone/check the repo and update the Pkgfile with the latest commit number. Then you can rebuild the package to ensure it still works, and commit your work.