I was following a youtube tutorial series, and it went over custom entities, but never touched on how to make them spawn naturally in the world. Can anyone help me with this? Everything works as far as the attacks, spawning from the custom egg and the loot tables.
Well you could read forge's official docs. They are not exactly a tutorial though.
Apart from that not really, I haven't seen any good tutorial. Even praised modders like McJty make numerous mistakes in their tutorials and enforce cargo-cult programming. I guess the best way to learn is to consult forge docs, look at some open-source mods that are trustworthy, look at vanilla and ask on these forums. I could recommend some repositories I've looked at and they look fine to me - here, here,