I want have this ability to select multiple items with checkboxes and delete them in one place.
This is the code:
<% @products.each do |p| %> &
1: You can create your own Ids by passing them as part of the options hash:
<%= check_box_tag "product_ids[]", product.id, false, :id => "product_#{product.id}" %>
For 2 and 3 I'd recommend looking at this Railscast.