With the Lions agreeing to try to trade quarterback Matthew Stafford and with Texans quarterback Deshaun Watson possibly asking for a trade of his own, it makes sense for an annual (or so) refresher on how trades work in January and February.

Teams can strike unofficial deals now; there’s nothing that prevents them from doing so. However, the deal won’t become official until the start of the new league year, on March 17, at 4:00 p.m. ET. That’s when both teams alert the league office to the trade.

And if one of the two teams decides not to proceed, the trade doesn’t happen...