I liked this tutorial, it has a nice example on the lack of memory of
web applications
http://www.troubleshooters.com/codecorn/ruby/rails/rapidlearning_rails.htm

I have been working with a controller code as such
   if params.has_key? :id
         @laststimobj=Stimuli.find(params[:id])
         @stimuliobj=Stimuli.find(params[:id].to_i + 1)
     else
         @stimuliobj = Stimuli.find(:first)
     end

with a form in the view
 <%= start_form_tag(:action => "hello") %>
  <%= hidden_field_tag "id", @stimuliobj.id %>
  <p>
      Name:
    <%= text_field("responseobj", "name", "size" => "20") %>
    <%= submit_tag("Name") %>
    <% end_form_tag %>

you can use
render_text params.inspect
in your show_next method to see what your parameter hash is like. I am
not sure if an action redirect can transmit parameters.