def show
   @user = User.find(params[:id])
  end

  def new
   @user = User.new
  end


  def additional_info
   @user = User.find params[:id]
  end


  def update
    if @user.update(user_addinfo)
        redirect_to user_path(@user), notice: 'User was successfully updated.'
    else
        render action: 'additional_info'
    end
  end


  def create
    @user = User.new(user_params)
    if @user.save
     #session[:user_id] = @user.id
     #UserMailer.welcome_email(@user).deliver
     sign_in @user
     redirect_to  additional_info_path(@user)
     flash[:success] = "Welcome to InYourShoes!"
    else
     render'new'
   end
 end

private

def user_params
  params.require(:user).permit(:name, :email, :password, :password_confirmation)
end


def user_addinfo
  params.require(:user).permit(:year)
end
end

<div class="row">
   <div class="col-xs-12 col-sm-6 col-sm-offset-3">
    <%= form_for(@user, :html => {:class => 'form-horizontal'}) do |f| %>
    <fieldset>
     <p>Do you have experience in Business? If yes, select one of the following:
      <div class="input-group">
        <div class="input-group-btn">
          <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown">Select one <span class="caret"></span></button>
    <ul class="dropdown-menu">
      <li><a href="#">Entrepreneurship</a></li>
      <li><a href="#">Investments</a></li>
      <li><a href="#">Management</a></li>
      <li class="divider"></li>
      <li><a href="#">All of the Above</a></li>
    </ul>
  </div><!-- /btn-group -->
  <%= f.text_field :year , :class => "form-control", :placeholder => "Years of experience" %>
 </div>
</p>

<div class = "center form-actions">
<%= f.submit "Submit", class: "btn btn-lg btn-primary" %>
</div>
</fieldset>
<% end %>
 </div>
  </div>

@user = User.find(params[:id])

def update
  @user = User.find(params[:id])
  if @user.update(user_addinfo)
  [..]

render action: 'additional_info'

def update
  @user = User.find(params[:id])
  if @user.update_attributes(user_addinfo)
  #your redirection
  else
  #your redirection
  end
end

def update
    self.additional_info
    if @user.update(user_addinfo)
        redirect_to user_path(@user), notice: 'User was successfully updated.'
    else
        render action: 'additional_info'
    end
 end