Re: Monitoring Hive Health
A bee diary is very useful, not only for monitoring internal things such as hive health but also environmental things such as timings of flows etc, which also affect hive health. I keep a diary for each location so if I'm wondering whether that hive that is low on honey will need feeding, I have the info to hand to know when the flow will start and if the hive can make it or not.
Re internal things such as hive health, when you are new a lot is hard to recognise. An easy one is relative mite populations because that can be reduced to an actual number via drop board counts. So if you kept data on drop board counts you will become familiar with seasonal fluctuations, which strains you have that suffer less from mites, and for hives that died, what levels they got up to before dying which may help you in future when deciding if you have to intervene to save a hive via requeening or similar. You will also know if after say, a year, your situation is stable, worsening, or improving.
Health issues that are not mite related, are mostly harder to quantify. However learn what you can and keep hard data where you can get it. That's what I do, anyway.
There is another philosophy that says you should not monitor mite levels or anything else, as you are not going to treat, so there is no point, just go by whether the hive is dead, or alive. But that was not your question, your question was what and how could you monitor, so that's what I've answered, as per what I do myself.
44 years, been commercial, outfits up to 4000 hives, now 120 hives and 200 nucs as a hobby, selling bees. T (mostly).