How to write rake tasks and set in crontab (rails 3)

rake tasks in rails3.0.5.rb

#via http://jasonseifer.com/2010/04/06/rake-tutorial
#via http://codequietly.com/2010/6/rake-tasks-101 - Basics
#via http://codequietly.com/2010/6/rake-tasks-102 - Advanced use of Rails ENV

#
# General Rake
#
namespace :twitter do
  desc 'Search Twitter for the parameter you pass in'
  task :search, :query do |cmd, args|
    # some very impressive search code...
    Rake::Task['twitter:search'].reenable
  end

  namespace :search do
    desc 'Search Twitter for "@daneharrigan" and save it in the database'
    task :daneharrigan => :search do
      # save results from :search and be happy
    end
  end
end

###
## The following code Finds Tweet of user and store in DB only once [Code is pseudo]
###

#
# Using Class
#
class TwitterStore
  def self.search(query)
    @results = Twitter::Search.new(query)
  end

  def self.latest_result
    @results.first
  end
end

# Twitter
namespace :twitter do
  desc 'Search Twitter for the parameter you pass in'
  task :search, :query do |cmd, args|
    Rake::Task[:environment].invoke
    # Rake is now aware of our Rails environment!
    TwitterStore.search args[:query]
  end
  # ...
end

# using Twitter Class
task :michealbenedict do
  Rake::Task[:search].invoke('michealbenedict')
  result = TwitterStore.latest_result
  params = {
    :username => result[:from_user],
    :message => result[:text],
    :tweeted_at => result[:created_at].to_datetime
  }
  #model
  Tweet.find_or_create_by_username_and_message_and_tweeted_at(params)
end

# crontab
*/5 * * * * cd /home/dane/twitter_store && /usr/bin/rake twitter:search:michealbenedict