From MacPorts to Homebrew

Here is my experience with transition from MacPorts to Homebrew

Prerequisites
RVM and Macports

Steps
Uninstall installed ports and remove MacPorts files (following official guide http://guide.macports.org/#installing.macports.uninstalling)

sudo port -fp uninstall installed
sudo rm -rf \
    /opt/local \
    /Applications/DarwinPorts \
    /Applications/MacPorts \
    /Library/LaunchDaemons/org.macports.* \
    /Library/Receipts/DarwinPorts*.pkg \
    /Library/Receipts/MacPorts*.pkg \
    /Library/StartupItems/DarwinPortsStartup \
    /Library/Tcl/darwinports1.0 \
    /Library/Tcl/macports1.0 \
    ~/.macports

Remove /opt/local from you PATH in your .zshrc or .bashrc

export PATH=/opt/local/bin:/opt/local/sbin:$PATH # delete this

Reinstall missing packages (that used to be installed from MacPorts) using brew. For example:

brew install wget coreutils

Delete old gemsets, reinstall rubies and gems using RVM. For ex:

rvm gemset delete <your_gemset>
rvm uninstall <your_ruby>
rvm install <your_ruby>
rvm use --create <your_ruby>@<your_gemset>
bundle install # or gem install <your_gems>