I suggest you take a look at rvm.
You can then set it as default with rvm use 1.9.3 --default
But if you are happy with your homebrew install.
Then just change the precedence of directories in the PATH
Here is my /etc/paths
# homebrews should always take precedence
/usr/local/bin
# the default stack
/usr/bin
/bin
/usr/sbin
/sbin
This is important generally for homebrew, else the system version of git, ruby, pg_admin,… will all be used instead of the brew version.
if you say which -a ruby you’ll see all the installed rubies, and the precedence in the PATH
eg.
$ which -a ruby
/Users/matthew/.rvm/rubies/ruby-1.9.3-p0/bin/ruby
/Users/matthew/.rvm/bin/ruby
/usr/bin/ruby
UPDATE: I now don’t think you should change /etc/paths
Instead you need to check which of .profile, .bashrc, or .bash_login is being loaded in your shell, and just add /usr/local/bin to your path.
For me, I only have a .profile. You can create that file if none of those files already exist in your home directory.
# homebrews should always take precedence
export PATH=/usr/local/bin:$PATH