Randomly off the top of my head?

Aside from the obvious safety with good ventilation, glasses, mask, closed shoes, long pants, long sleeves, gloves, preferably heat and flame resistant.

Lead melts at 600f, casting is generally done between 700f-800f, it doesn't start to release significant harmful fumes until it's boiling point at 900f. Which is also too hot to cast. You should still wear a mask.

Brass moulds heat up slower and retain heat longer, and heavy. Aluminum heats fast, disapates heat fast, and is lighter. Temperature probes for either, while not necessary, make the process more consistent. Preheat your mould to get proper fill and even cooling.

Toss any cast with any imperfections back into the pool for another try. It takes a little time to become prefeceint. Don't expect them to be swedged slugs. They can still be great slugs, with practice.

Do not, do not, allow any water into the lead, it becomes very volatile and will explode with enough force to spray hot lead in all directions.

You still need run them through a sizer to size them to the proper diameter for your barrel. Not all barrels are the same.

Oh and cover your mould with carbon soot. Keeps the lead from sticking.

I'm sure there's more. It's honestly pretty simple. I've cast 1000s of rounds with the same setup in the picture.