Every colony needs a queen so you need to find her in every inspection. Many new beekeepers have difficulty finding the queen. Remember, a large, well-bred queen is easier to see than many of the small queens which result from swarming or emergency replacement by the colony.
You may need to find the queen so that you can:
Mark her to make her easier to find at future inspections.
Determine that your colony definitely has a queen. Of course, if you miss her but you see eggs you know she is there.
Make a nucleus, either queenless or queenright.
Make an artificial swarm.
Make two hives from one.
Restrict her to a particular area such as a Jenter comb box in order to produce larvae of a known age for grafting.
Remove her prior to introducing a new queen or queen cell.
Remove her as an emergency measure to delay a colony from swarming.