Ask! The most effective band sites specifically direct members to the store from their homepage. This "call to action" can be as simple as an image of your album on your front page with a link to your store. To see some great calls to action, check out Chris' blog post on the topic.
Make it easy Once fans hit your store page, make it easy for them to buy. Don’t clutter the page with other features. At most, a paragraph or two thanking fans and providing any important info about your products is all you need.
Free shipping Big online stores have free shipping for good reason: it is proven to increase online sales. From experience, this works for bands as well. Though you will need to pad your products by a few dollars, the end result of having an all-inclusive price is worth it.
Offer something more Throwing in a freebie like a downloadable track with a CD purchase is another great promotion. Bandzoogle makes this easy; payment receipts include the fan's email address. Use that to send them a track using the Album Download feature's "send a free track" function.