A good way to keep regular visiting customers is a create a forum sponsored by your site using a different name. This forum should be related to your websites business category in some way.
The other way is to create a blog with regularly updated articles. Search engines like rss feeds and live content. I have setup a wordpress blog about green issues and reviews and tips about being green. This will accompany my main e-commerce website which sell eco-friendly cleaning products.
I have found that everytime I write an article it gets lists almost instantly on google as search engines like feedburner and technorati pick them up.
Then place links between the two sites, like product reviews and buy this now.
have a look
www(dot)greenmop(co)uk and blog(dot)greenmop(co)uk