@to the opening poster , why don't you just call upon his assistance or presence ? You don't need a spell to call a diety to your side and you wouldn't need a spell just for him to be with you .?
And summoning a diety ? Seriously? I frankly think you are not treating them with enough due respect..they are not a mere spirit just for you to summon whenever you wish an the act of summoning can be seen as rather rude to the being that is summoned .
I have read a lot of different methods, mostly nonsense. Pazuzu is human friendly and will come if you call. I know very little about demon summoning but I got a copy of his sign and sat down in a quiet room, low lighting and called for him several times, quietly. He answered me quite quickly and I asked him for a couple of favours in return for something he wanted from me. I agreed and within hours the things I asked for started to happen. Not in exactly the way I had expected but the result was the same. You just need the desire to contact him and be able to listen for his reply. I am just waiting and watching for the next thing I asked for to start to happen. I would encourage you to try and keep it simple and straight forward. Be respectful and truthful and you will be ok.