That is a very general question... But the devil your probably mean Demons... Let me tell ya, if you want to call Satan, Lucifer, Asmoday or any of the deadly sins it's not going to work...
An easy method would be the Ouija board. You should be carefull though, if you do a generall summoning anythig could show up... The end may not be preety... It depends... Just take or make a Ouija board and a plachette (if you don't have one a shot glass can be a good option)..later spin it three times and just call for the Demon you desire. This is a formal summoning which means he spicific one will come (if they want).
Good luck ive tried every spell on here including ones that say
Dont chant this more than once well i have and nothing which makes
Me think thats you either cant summon the devil contrary to what
People have written on here or he doesnt come to Australia to make pacts i even tried to summon ragoo but no luck either
So if you manage to do it good luck but please let me know how you did it
Oh, contract! Sorry, I read "contact..". You have to actually summon the Demon or any entity...and make a deal with them. You should clarify what you earn and what you will give to each other. I wouldn't suggest to make a deal with a Demon you don't know well....