I got started with 2 packages of bees in very late Spring this year.
Some things I learned that have mostly already been mentioned in this thread or other threads....
I put 2 medium frames of wired wax (no hooks) in the middle of each brood box thinking that would act as a "guide" for the bees when they started building on the other 6 frames which were comb guide frames from Walter Kelley. In retrospect, I could have just used all 8 comb guide frames and kept a close eye on them for the first few weeks to correct any errant comb building.
I spent time and effort "painting" beeswax on the comb guide triangles of the top bars. This was completely unnecessary. The bees did not seem to care about it.
I think the biggest mistake I made was not realizing that I needed to push all the frame together in the center of the box so they make a single unit with proper beespace maintained between frames at all times. I overlooked this detail and it contributed to frames having lopsided combs thicker on one side than the other and some having a "double" row of comb hanging down from the same top bar. It was not until about a week ago that I figured out my mistake and that I could have prevented it by pushing those frames together from the beginning instead of thinking the frames had to be equally spread out from one side of the box to the other. (I was told recently that 8-frame boxes don't all have the same width dimension either.) When I get packages in the future, I will keep the frames pushed together and see how that works out instead.