Several online shopping portals are offering bonus miles right now. Start your shopping on their site, click their link to the store you’re going to buy from, and earn miles for the purchase.
It still pays to check to see which store offers the best deal at the merchant you’re using. I frequently start my shopping at EV Reward, searching the store I’m going to use, and comparing how many miles (or percentage cash back) I will get for the purchase going through different shopping sites.