Most books I've read about the Goetia tell you to give the offering once the demon has brought you the result you asked him/her for. But what about giving the offering in advance at the moment of evocation? I've read a couple times online that this could be a way of showing the demon that you trust him/her. What are your thoughts? Have you tried this method before?
Do you trust him/her? If you do, why? You really shouldn't be trusting any entities that you don't have a lot of personal experience with. Even there, I wouldn't exactly say "trust" is the right word. Also consider, if you do not fully, truly trust that entity, I wouldn't recommend starting your relationship by essentially lying. Know what I mean?