Here are two photos of queen bees. One photo is from Hive A (that will mean something to those of you who have been following the 2017 beekeeping season on www.friendswithgardens.com). The other photo is the queen from Hive B. Once you see them, you can't unsee them.
And that is the best way to learn to spot queen bees in your own hive. Look at photos so you know what to look for: the short wings, the extended abdomen, the large dark spot on their thorax ... and so forth.