It is not easy to find a queen bee, which is something you want to do in some beekeeping operations like swarm prevention, splitting a hive, requeening etc. Here is one simple approach.
Step 1: One Step Procedure!
Find the queen. Take the frame with the queen out of the hive. Hold it in one hand or put it on the lid of your hive. Work carefully and slowly. You do not want to squish bees or even worse, injure your queen. She is the future of your beehive. Use a marker which is an oil paint based one, my one was some Japanese brand. Move slowly as fast moves of your hand will make the bees and the queen nervous. I think the smell of the marker bothers the queen, so I try to approach her slowly so she gets somewhat used to the smell. I follow her with the marker and wait until she stops to do her thing. The point of the marker approaches from her rear, lets say under an 45 degree angle, slowly and carefully press the pointer on her back and make a small dot. This dot will maker her much much more visible, so whenever you need to do some of your beekeeping stuff, you will be much faster, and more efficient. I dont think that it has any bad effect on the bees or on the queen.
Step 2: Youtube Video of the Queen Marking