searches_controller

  def search
    @video_results = Video.find_with_index('#{params[:search][:search]}',{:limit => 10})
    @user_results = User.find_with_index('#{params[:search][:search]}',{:limit => 10})
    @topic_results = Topic.find_with_index('#{params[:search][:search]}',{:limit => 5})
    respond_to do |format|
      format.html
    end
  end

topic.rb

  acts_as_indexed :fields => [:name]

user.rb

acts_as_indexed :fields => [:name] 

Video.rb

acts_as_indexed :fields => [:title, :description]

view

<%= simple_form_for :search, :url => search_path, :method => :get do |f| %>
    <%= f.input :search, :label => false, :placeholder => "Search... (press Enter)" %>		      
<% end %>