You need to know who you want to contact or at least what religion or area of belief. Then research those deities, look for which one your like to contact for what ever reason you have. Then research the best ways to contact that diety, how to do it right, respectfully, and to get the best results. Once you have all of that info you're all set to contact them.
Different deities require different methods of contact, and you're own ability to do certain ones is a point to consider. For me meditating isn't easy for me, so I use my dreams a lot and other forms of communicating. Good luck!