To take advantage of the promotion, you'll need to present a coupon (i.e. show the coupon or a screenshot of it from your phone) when ordering (the promotion is only good in-store). You can find the coupon on their social media accounts (including Facebook and Twitter).
The $5.99 Footlong sub deal is good at participating locations across the US (except for Alaska and Hawaii). As with most such deals, I'd advise calling ahead to check to make sure your local Subway is participating.
Photo via Subway.
