How do you create a runescape private server from scratch

Dont. Its an illegal copyright infringment. so unless you like prison, i'd advise against it.

^ False. Creating a RuneScape Private Server is not illegal and it's a fun thing to do. Decompiling Jagex's webclient's code and models would be illegal however. Jagex never takes legal action against 317-474 revision RSPS's that only have around 30 players.. Jagex only cares about the newer revision RSPS's that have a lot of players.