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).
Other ways could be channeling, or divination.