Re: Beginner's mistakes
Yes - many good points.
Quite often I read of beginners inspecting their hives every few days, or weekly. As soon as there are eggs & capped worker brood ( a viable queen), make that once or twice a month at most, especially with a new hive . Another mistake is splitting a small new brood nest ( putting a frame of foundation in the middle) in an attempt to help them build up faster. Wait at least until they are hatching out the 3rd brood cycle ( about 2 months).
Don't mistake "checker boarding" as a technique for expanding the brood nest ( don't alternate foundation between brood combs to "give the queen more laying space".) Once you get a few years behind you, there are some brood nest manipulations that are successful, but leave it alone to begin with.
If you want to see what's going on inside the hive - get or build an observation hive. It can be an emergency nuc, in the worst case. I ran one for several years, early on, and could surmise what was happening in the other colonies by what was going on in the OH. It eased my desire to go mucking around for no good reason, and let the hives build up naturally with minimal intrusion. I learned to watch and enjoy flight activity as an indicator - like KC mentions.
You can probably never have enough bottom boards, covers and spare supers - try to get or build a few extra whenever you can. I was lucky in the beginning. All we had to worry about was tracheal mites and foul brood and nosema. There were usually more swarm calls than equipment.
After 40 years of beekeeping, I've come to realize that the bees can fix most of my mistakes.