Your Service Provider need a single top right login link or button. Apparently it could seem not important. Actually it is the one of the most effective ways of helping users and improve the user experience.
The best practice is to put in your home page and in every page a single link to the login page. The link must be labeled login. The link must be always placed on the top right corner of the page.
References and further readings
- 4 simple steps for successful federated login, http://discovery.refeds.org/guide/#login, 19 NOV 2013
- espresso: Establishing Suggested Practices Regarding Single Sign-On, http://www.niso.org/workrooms/sso, 19 NOV 2013