Some journal homepages will have an option to set-up an email alert or have a RSS feed as a way of letting you know when a new issue is published, and what's listed in the table of contents.
However, not all journal offer this, so there are a couple of services that specialise in providing table of content alerts and RSS feeds:
institutional login procedure.
Creating Zetoc Alerts:
Zetoc RSS Feeds:
More help on using JournalsTOCS.