In these challenging economic times email needs to remain the go-to tool in your marketing toolbox. Why? Because it has got the best ROI out there. According to the Direct Marketing Association, email returns over $40 for every dollar spent—that’s twice the ROI as the next best medium, non-email Internet marketing. Still, the trick is to get the most out of your email marketing efforts. Here are the top-10 tips that I’ve used at Genius.com to do just that.