Heston is spot on. The maximum difference between altitude of the airborne starting and the end landing point must not be more than 1% of the distance flown. A field landing is also more than acceptable, as long as it is far enough away. For those being launched by aerotow, the tug driver also has to say where and how high he dropped his victim off. A winch launch simplifies things.
Returning to the OP, a hill in the middle of a field is often quite a good thing. Land at the edge and roll up the hill to stop. Landing uphill also does a good job at killing any float. Ask pilots from Dunstable about that. As for crashed gliders, I've apparently been involved in lots of them. Concerned members of the public call regularly call the police to report an incident. It's quite good really because if you did actually spang it into the ground, it would be nice to found sooner than later. Generally though, it turns out to be a waste of police time.
I just hope nobody tells the press that gliders regularly "crash" into fields on purpose.
PM