Install Rails as you normally would. Use sudo if you would normally use sudo to install gems.

$ gem install rails

Generate a Rails app as usual

$ rails new myapp
$ cd myapp

Run the server. Bundler is transparently managing your dependencies!

$ rails server

Add new dependencies to your Gemfile as you need them.

gem 'nokogiri'
gem 'geokit'

If you want a dependency to be loaded only in a certain Rails environment, place it in a group named after that Rails environment

group :test do
  gem 'rspec'
  gem 'faker'
end

You can place a dependency in multiple groups at once as well

group :development, :test do
  gem 'wirble'
  gem 'ruby-debug'
end

After adding a dependency, if it is not yet installed, install it

$ bundle install

Don't forget that non-Rails commands must be executed with bundle exec

$ bundle exec cucumber

When you're ready to share your application, lock down your dependencies to the specific versions you are using now. This will ensure that other machines use exactly these gems, and are not affected by new releases of gems in the interim

$ bundle lock
$ git add Gemfile.lock

After locking your dependencies you may not modify the Gemfile without unlocking first

$ bundle unlock

If you've updated your Gemfile and want to install the new gems and re-lock once the new gems are finished installing

$ bundle install --relock