class User < ActiveRecord::Base
attr_accessible :email, :name, :password, :username
validates_presence_of :email, :name, :password, :username
end

class SignupController < ApplicationController
def init
    @user = User.new
    render :template => '/signup/signup'
end

def signup
    @user = User.new(params[:user])
    if @user.valid?
        @user.save
        render :template => '/signup/success'
    else
               #bla bla bla
    end
end
end

<h1>Signup!!!</h1>
  <%= form_for(@user, :url => signup_path) do |f| %>
   Name: <%= f.text_field  :name %> </br>
   Email <%= f.text_field :email %> </br>
   Username: <%= f.text_field :username %> </br>
   Password: <%= f.text_field :password %> </br>
   <%= submit_tag "Submit" %>
  <% end %>

<h1>signup successfull :) </h1>

get '/index/signup' => 'signup#init', :as => :signup_index
post '/index/signup/' => 'signup#signup', :as => :signup

gem 'strong_parameters'

class User < ActiveRecord::Base
  include ActiveModel::ForbiddenAttributesProtection
  validates_presence_of :email, :name, :password, :username
end

class UsersController < ApplicationController
  def new
    @user = User.new
  end

  def create
    @user = User.new(user_params)
    if @user.save
      redirect_to login_path, :notice => "You have signed up successfully. You may now login!"
    else
      render :new, :alert => "There was an problem creating your account"
    end
  end

private

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

<h1>Signup!!</h1>
<%= render :partial => "form" %>

<%= form_for @user do |f| %>
  <%= f.label :name %>
  <%= f.text_field :name %><br />

  <%= f.label :email, "Email Address" %>
  <%= f.email_field :email %><br />

  <%= f.label :username %>
  <%= f.text_field :username %><br />

  <%= f.label :password %>
  <%= f.password_field :password %><br />

  <%= f.submit "Sign Up" %>
<% end %>