How to make sure your site is always accessed over https
Force access over ssl (https)
You can force access to your site so visitors always use ssl (hence the connection is made over https). This is a very simple setting in the Joomla Global Settings. Just go to System > Global Configuration > Server.
Your needs may be different from mine, but it's a good idea to set the "Force SSL" setting at least for "Adminstrator Only". If you want to get all your traffic over SSL just set it to "Entire Site".
Don't forget to save your settings - clear your cache - and you're done!
Why should you use SSL - even if you're not an e-commerce site
It's a good idea to use SSL for your site, even if no "sensitive" data like credit card data, payment data or whatever financial data are part of it.
Using SSL will show your users you care about security and as a consequence your users will get additional trust in your site. Moreover, it's no secret that a lot of people use the same password for all the websites they visit: they figure out a real difficult one, based on a sentence they can remember and with substitution of some alphanumeric characters by special characters.
BUT ... if a hacker catches this password somewhere on a (your) site, (s)he can use it and try to log in to other sites the user visits, so a hacker can take over the electronic identity of your user. Moreover, if your user also uses this single password for logging in to sites where they manage their financial data, I think it's easy to figure out the importance of using SSL for access to your website.