The primary thing that brings people back to any website in new content, while old but unseen content may as well the numbers are not as great. For this reason it is a good idea to have immediate access to new content on your home page. Not only this it should be in a place in which the viewers attention is immediately drawn to.
One way to do this have you have likely seen is a news feed, which is a slides show that cycles through various new features over the duration of a minute or so. One nice thing about a news feed is that it doesn't take up too much space and allows people to see the rest of the website as well.
Alternatively a simpler yet often just as effective way to do this is a summarized version of an article or whatever it you have added with a read more/see more link. This allows you to catch the viewers attention once again without taking too much space.
The last and least intrusive way of doing this is having a link on your main site, saying something like new content or recently added.
There are of course other ways to display your new content including right on your main page but these three are some of the ones I have seen used most effectively and do not require extensive changing the home page regularly.