If you want to train a ghost you must have a subject after which to model the ghost. Find someone who takes your breath away. Maybe it will be that girl who sits across from you on the subway, or it could be a close friend that you've always wanted more from.

Make memories with them. Memories that won’t easily fade. The kind that come to you in the darkest hours of the night. Learn all the little things about them that you possibly can. Every endearing detail and quirk that makes them a unique human being, and love them to your own breaking point. It doesn’t matter if they return your love. Some even argue that its better if they don’t. This way you know that they will be the one to leave you, but thats just a matter of opinion.

Take little pieces of them and stow them away in your pockets. Hide some of those pieces in the music you listened to while you were with them. Take another and put it in the walls and under the floorboards of the places you went together. Stain everything you know with their memory. The best ghost trainers can do all of this without ever speaking a word to their subject.

Eventually they will leave you. It will be quick like when the sun shines through the clouds on a dark day before hiding his face again. There will be no real explanation. Don't you know there is no law for such things? Now the ghost will begin to take shape, and if you have followed each instruction carefully you will never be able to escape.
*~W.C.