To answer your question directly: do not create a controller for the general layout ... But follow the tips below:
1 about.php, index.php, sign-up.php.:
aboutand indexactions can be collected in the controller, as a rule, I call it Static.
Thus, logically representations will be in /app/views/static/
sign_up : User. , Registration.
2. common/ header.php, footer.php, scripts.php :
layouts/_header.html.erb, _footer.html.erb, _scripts.html.erb + , .
3. scripts/jQuery.js styles/main.css /public/javascripts /public/stylesheets ( , Rails 3.0.x)