You box up the item using the original packaging, slap on a return label printed off Amazon's website, and drop it off at UPS (a box or a store). Item arrives back at Amazon, and your account is credited.

I've only done it once. It was a defective milligram scale costing in the low teen 2-digits, which arrived DOA. Taking a chance, I resubmitted my original order and dropped off the defective unit at the local UPS store. A couple of days later, I had a working scale and an account credited to reflect the purchase of one scale, net.

I don't live in the US and have never made an Amazon return. I was under the impression though that they organised for a courier to picking the package from you, rather than you having to go and send it?

Returns though lockers. You don't like it, you bring it to a locker (ie 7-11 or college campus) and Amazon will eat the shipping fees.

I've never had a return challenged or refused, and I can immediately print out a shipping label. It's not entirely "no hassle", but it's the least I've ever had, and the only reason I've ever purchased "risky" merchandise (e.g., clothing) online to begin with.