He started planning as soon as he started to think he "wanted to kill..."(263). Wargrave wanted to "commit a murder"(263), but "The innocent must not suffer"(263) so he made sure this happened. After his first victim was chosen, "A childish rhyme of my infancy came back into my mind"(264), this was the start of his plot, as him, the mastermind, and the puppeteer.
He lured his victims to the island by sending letters or wires, apparently sent by friends, colleagues, or old acquaintances. Inevitable... their deaths were inevitable, all life has an end, but Wargrave wanted to take it step further... he wanted them to suffer accordingly for their misdoings. Wargrave hated criminals and took "no pleasure"(263) in seeing an innocent man in his court room, but he loved to "...see a wretched criminal squirming..."(262), he has to "...protect the jury..."(263) from emotional appeals and good impressions, the jury's job is to determine who was guilty, and who was innocent, Wargrave made sure this occurred.
Wargrave's judgment in the courtroom slowly slid... he didn't recognize his pleasure in inflicting death as he used to before he thought of himself as "God Almighty"(153). "...the lust to kill."(261), one of Wargrave's talents, he also knew how to manipulate people's thoughts, and their emotions without their knowing so as he did