Belial seems to like you to show some backbone, you may have read an old post I made here which describes that the first time he came into my life he attacked me, to see how I would react, and then (it seems) based his continued presence in my life on the fact I had to kick the butt of his army - a task I suspect he made achievable for me, although it wasn’t easy.
He’s shown a distinct preference to be evoked outdoors, there’s a small grove of trees nearby that has mist rising for a while after sunrise most days, and when I evoked him there one morning, he manifested some forty feet tall in that mist; when I subsequently summoned him indoors, he mimed that he found it cramped, so if at all possible, conduct this outdoors?
He doesn’t seem to be a stickler for more formal dress (King Paimon and Azazel, and Thoth, have all requested this, formal robes or at least fully clothed) - Belial doesn’t seem to give a hoot if I’m wearing a ratty old t-shirt and no knickers, and unwashed after a night’s sleep. He may be different with men, but I doubt it.
He enjoys being offered things you wanted for yourself, such as half a tub of posh ice-cream I was saving, which makes me think the emotion of sacrifice is more important to him than superficial flashiness - kind of like the story about the widow’s mite.
I’ve offered him reddish-coloured things and he likes those, and he’s also said he’d very much like me to engrave his sigil in metal, aluminium in this case, so that might be a payment to offer him if he comes through with this important task?
Don’t offer it beforehand, he seems hard-headed and not the type to expect something for nothing. And don’t offer him anything unless you mean for it to become his.
He seems to dislike all things connected to empty status, he also seems to dislike any kind of racism, snobbery, classism, any effort we make (based on real or imagined criteria) to set ourselves above another human monkey such as ourselves. This has been my experience but it’s also described in the Imperial Arts entry here, and that dude has a very different approach to me, and yet we received the same basic information.
This may be important - if you’re speaking about the financial future of your family, the desire for your children to be higher status than others may leave him cold, whereas the desire for power is something he’s entirely understanding about.
The Imperial Arts guy mentions in that blog that he got the impression Belial sneered at him, I’ve seen the same response but (for whatever his real form may be) the sneer or smirk he sometimes displays seem to me to be more the astonished amusement of a being totally outside human life, necessities, and desires, who hears the outrageous and ridiculous wishes of humans which must seem as surreal to him as the grimoiric descriptions of spirits who can make birds appear, or who ride camels and tigers, seem to us.
When Aaron Donaghue, who believes all spirits in the Goetia are aliens, attempted to remote view Belial, he was shown an image of a dead alien in a crashed spaceship - I believe that was Belial’s sense of humour showing through, to be honest! 
I did some work deconstructing his enn into Enochian, here, and his name, here - I can’t claim those are canonical and I’m not a language expert, but I think they offer a different slant on the traditional interpretation of his name.
I am extremely fond of Belial, as I posted here, but he’s informed me many times that he’s not a “friend,” and will only work with you if there’s something in it for him, so don’t try to plead to his sympathetic side