I don't think you can specify a final gravity in advance, it depends on where you started and what type of yeast you're using. I'm new at this, but I gather that it's not uncommon for cider to drop below 1.000, so even that point doesn't guarantee that fermentation is complete. The safest thing is to measure it when you think it's done, then measure again a few days later. If the readings are the same and they're near where it ought to finish, then you're done. For a cider (not a crazy OG apfelwein), I think that'd be expected to be at or below 1.000.
I'm assuming here that you're going for a totally dry cider. If you're going to stop it before it dries, you can choose the FG as you like. If it has stopped on its own and it's far above 1.000, you likely have a stuck fermentation that will need attention. The magic number I see tossed around for stuck ferments is 1.020, although I don't know of any reason why that would be a magic number. Certainly any cider ought to complete well below that, though.