Step 1: Install XCode Command Line Tools

xcode-select --install

Step 2: Install and prepare Homebrew

ruby -e "$(curl -fsSL https://raw.github.com/mxcl/homebrew/go/install)"
brew doctor
brew update

Step 3: Install rbenv

brew install rbenv ruby-build openssl
echo 'eval "$(rbenv init -)"' >> ~/.bash_profile
source ~/.bash_profile

Step 4: Install Ruby

Most people who have spent any time using the command line have learned to use vim well enough to edit conf files: moving the cursor, entering insert mode, and saving and quitting the file :wq. I know because I was one of those people for years. It wasn't until I found a few magical commands that I truly understood why vim was a true competitor in a world of IDE's and Textmate clones.

A while I ago I posted about an efficient way to do find and replace in files.

:args `ack -l keywords`
:argdo %s/keywords/replacement/ge | update

Step 1: Install and prepare Homebrew

ruby <(curl -fsSkL raw.github.com/mxcl/homebrew/go)
brew doctor
brew update
brew install apple-gcc42

Step 2: Install rbenv

brew install rbenv ruby-build openssl
echo 'eval "$(rbenv init -)"' >> ~/.bash_profile
source ~/.bash_profile

Step 3: Install Ruby

rbenv install 2.0.0-p0
rbenv rehash
rbenv global 2.0.0-p0
rbenv shell 2.0.0-p0

Here is the most modern approach to gem crafting with Bundler:

bundle gem your_gem
cd your_gem

edit your_gem.gemspec and add description, summary and optional website. Add required gems such as rspec to the Gemfile.

rspec --init 
touch spec/your_gem_spec.rb

Write good tests. Add your code to lib/your_gem.rb. When you're finished its time to build and push to rubygems.org: