Types of things that attract different audiences.

What would motivate someone to buy/read a particular magazin?

Well to be honest it all depends on the persons interest. If the magazine is pitching to them then ofcourse theyd buy it.
-artists
-content
-main story
-layout,colours,fonts
-visual codings
-physical
secondly if the lay out of the magazine is attractive e.g. it has all the aspects to attract the person: photos, sell lines, events, adverts etc.

What makes a good front cover

Things such as the cover star. If the cover star appeals to the audience then that will make it a good cover. Also things such as the colour and font will reach out to the target audience.
Good sell lines that have impacts.
-Cover story that makes people think.
-wording of headlines