First, do no harm. Don't mess up the integrity or alignment of the frame, break any parts, bend the fork or bars (worse than the may be), lose any of the screws, sell off the parts before you really know what you want to do in the build. Don't tighten the bolt on the front of the leather saddle. Don't separate the chain with a chain breaker if you don't have experience or you get a book or a few You tubes about how to do it. Don't just dive in and true the wheels or tension the spokes. Check that your seatpost is not too small or too loose for the seat tube collar or pinch bolt, before diving in with a ratchet wrench and starting to (OVER) tighten it.

Apologies for making this a big pile of negatives. I've been wrenching on our bikes and strays I bring home for maybe 50 years now, and I still have to tell myself some of these things, as I want to dive in and start pulling things off.

Other than that, just recognize your problems and questions, and use the experts to help you solve them. Looks like you're on that track!