How do I help a dead spirit appear to me?

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Laugh if you want because I'm not joking, I will start by telling u that. This is in relation to my other thread "My dead best friend is haunting me", you can go there if u want the full story but here's the bridge: Long time best friend killed himself, he said it wasn't supposed to happen, he knows he's dead now but is still in shock, he's using my girl to communicate with me although he feels bad about it tho. She can only hear and see him. He's slowly learning to do new things, before he couldn't hear me but now he can, I just can't see or hear him still. I need to find out how he can appear to me and talk to me so I can hear him cuz he said he has no control over those things, when he appears, etc. He doesn't know how yet. Does anyone know anything about this stuff? I know that's a stupid question but I just thought I'd ask and see if someone knows something. He's been hanging around my girl cuz he's bored and only she can hear/see him, but if I'm able to, he'll be around me and won't have to bug her and she won't feel cold/weak/drained when he's around. Does anyone know some trick they've heard somewhere? Something? Anything about the "rules" of the spirit world in order to help him appear to me, etc.?