He enjoys blood, and will hint if he wants yours. A few nights ago as I was putting on his sigil pendant, I softly itched my leg. It started to bleed with no pain and the blood pooled into the shape of an eye before I even noticed I was bleeding. I took the hint and covered my pendant with it. I slept better that night than I have in a long time and was covered with an amazing soothing warmth all night. 
I’ve found this to be true. It’s a form of telepathy and if they are interested or already working with you, they usually answer. It however may not be instant, and proper evocation will get you a stronger experience.