The Belgium striker was taken by surprise when Chelsea told him he could join another club for a second season running.
West Brom, who he had a successful stint with last season, soon joined the running for his signature, but a chat with Martinez and Mirallas - in camp with Lukaku at the time - made up the 20-year-old's mind.
"It was a crazy evening. I was sitting in my hotel room in Brussels when the phone went to tell me I was going out on loan again. It was 7pm, and that was the first I knew of it," said Lukaku, who spoke to the Belgian media as part of the build-up to Friday's match in Glasgow.
"There had not been a mention of it before then, but after speaking to my parents, I decided to take the plunge.
"Different clubs called me and I had to take the right decision. Roberto Martinez called me for 30 minutes and explained me what he expects from me.
"I decided that Everton was the best choice. They are a more prominent club than West Brom, where I had a good time. The important thing, at 20, is to be playing, and while West Brom was an option, Everton was a better one.
"I've also known Kevin Mirallas since I was 14, and that should help. We talked about [the loan move] and I am looking forward to playing."
Chelsea manager Jose Mourinho had indicated when taking the job for a second time that Lukaku was in his plans.
The striker played in Friday's European Super Cup loss to Bayern Munich - missing the crucial penalty - but has been deemed surplus to requirements for now.