First thing I do when I enter the apiary is to watch the fronts of the hives--notice how many bees are coming and going, are they bringing in pollen, nectur? are they thousands of bees at the enterance fanning? Few or no bees? This seems to tell me, If they are having problems. Then I do a deep inspection on any hive that is not doing as well as it was the last visit. I will break it down to the brood chamber and see if there are brood,eggs, etc.
If there are lots of bees coming and going, (normally for that hive)I just check to see if they need more supers..
As stated above--keep a record of your hives and study them each.. Get used to what is normal for that hive and you'll know at a glance what needs to be done and when... Good luck