You probably want your login screen to be https, so that users are sending their passwords to the server as clear text. You should have a welcome page first.
As far as how to access some pages through http and some through https, just have both http and https connectors enabled. Make sure that all the links for your secured pages use https and the correct port number and it will use the https connector for those. If you enable the redirectPort on the HTTP connector and set the port to the same port as the HTTPS connector, then all secure requests will get redirected to the HTTPs connector.
user are -> users aren't