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.
Most importantly, don't look at every bee on every frame. Look at the frame activity as a whole. Look for something different. Most bees will be in one place, or will be working from side to side. The queen bee tends to travel, and she can move fast! She is also likely ringed by attendants, many of whom will be facing her. Learn to spot that pattern and you will find your queen!