Thomas,
There is one thing that will help a magazine type site IMO more than anything else: Original quality content that people are looking for. We build sites, do SEM/SEO, etc. and I never cease to be amazed at what happens when one of our copywriters seems to write the "perfect" piece for one of our clients. It does not matter that the on page SEO was not perfect, etc. All of a sudden we are seeing the piece on different sites and in news feeds and we did not use some press release or other mechanism. One person picked it up after another and all of a sudden it was out there.
If you concentrate on this and then provide a way to stimulate/tickle the reader along the lines of say a highly known sports site (ESPN, Sports Illustrated, one I have just begun to marvel at is The Bleacher Report) people will have more reason to stay on and go through your site. Just go to one of these and look how often a given story teaser appears on a single page. Have teasers that attract attention: If on the NBA page, see what is there about specific teams, on a team page specific players, etc.
Lastly, a client of ours has probably taught me more about the value of an image than anyone ever. He was unbelievably strong in how many, where, quality control, etc. on his site. As the result, he has a site with a ton of traffic much because of the images (not a mag type site though). So, look at successful magazine to web sites and learn from them.
The one concern is "they make their money primarily through advertisements...," make sure the good is not the enemy of the best. Many business people fall prey to the "if we take that off, we won't have the revenue..." line of thinking. Too much advertising will cost you in bounce rate and time on site. It must be advertising that fits the visitor and it must not be so obtrusive as to be annoying. I once let my online subscription to a major newspaper that I truly enjoyed because the way the began doing ads kept interrupting any chance of finishing an article.
Later they dropped that mechanism; I never went back.
Good luck,