Landing in inopportune places is an unavoidable part of HABing. Just last week, we landed 30 ft up a tree in the middle of some really dense thicket.
Don't let that discourage you though! Recovering payloads is part of the fun, and some really great stories come out of it.
If it lands on private property, you should talk to the owners of the property before venturing out for retrieval. I've never had anyone not let us retrieve a payload, and most people are very friendly and will help you look. If possible, it's good to have a ladder and pruning shears on hand, in case it lands in a tree.
If it lands in a place that you can't immediately get to, make a note of the last known coordinates/location.
As for the predictions, you won't be able to predict 100% where the payload will go; it's just meant to give a rough idea. I know that the habhub predictor and the Michigan predictors are reliable. In addition, don't worry too much if the predictions change every day. They're based on weather models that get updated several times each day, so they're supposed to change throughout the week. It's good practice to run the predictions several times the day or two before launch, and at least once more right before launch.