September 2019
@mckennaelise530, do you play with any Mods or Custom Content (CC)? If so, this could be affecting your gameplay as we just had several updates in the past few weeks and anytime EA updates the game, Mods/CC can become outdated and cause problems in the game. 
@mckennaelise530, &@themastergamer43 , the guide says that ghosts come out sometime after 10 pm until around 6 am. Ghosts won't come out all nights, but they will eventually come out. Whatever you do, don't choose the "Release Spirit to the Netherworld" as that will make it impossible for them to visit.
You should definitely strengthen their ties to this world (forgot exactly how this is worded, but it should be obvious.)
I also have them mourn a couple times a day. I've seen ghosts return from outdoors gravestones and indoors urns. Having strangers mourn them isn't necessary.. it can't hurt though so if you want to try it, it might help. 
But you can mourn gravesite with just your household members and still get a ghost to visit. I have my Sims mourn at different times of the day... I don't know if a certain time is more effective, but since ghosts only appear at certain times at night, it might help, and it can't hurt. 
I've never heard of smashing a dollhouse in front of a grave... might work for mean ghosts or ghosts that hate children, but it certainly isn't necessary!
Eventually your ghost will come out of their grave for a visit. You can interact with them then, and build up rapport with them. If your Sim regains friendship with them they will have the option to become playable.:eahigh_file: Then you can worry about the Ambrosia, or the Book of Life to get them to be brought back to life. But it is best if you use these methods to bring them back to life that you start working on your cooking skill or writing skill right away! (I would recommend the Book of Life as it is easier because you don't need special hard to get ingredients!)
If you have Realm of Magic, you can both call forth your ghost and resurrect them with certain spells. The one to call them forth from the grave is called Necrocall. The one that will return a ghost to a regular living Sim is called Dedeathify. Using this spell, you don't need Ambrosia or the Book of Life.
Please update us on your progress! Best of luck!
