Stray farm animals can be a danger to themselves and to humans. Leave nothing behind you but your footprints, and that includes biodegradable matter such as teabags and orange skins. The chances are your charming scraps won't be native to the area, and may not be very welcome by the ground. Dress for the occasion. Footwear must be adequate and waterproof, as must be your clothing.
Weather can change dramatically, so be prepared for any eventuality.
Bring plasters for your blisters. Splatter yourself with sun cream if there's even a hint of sunshine, as you could be exposed to the elements for a long time. Bring plenty of water. If you want to drink out of a stream make sure that it's very cold, and running freely before you glug. Always tell someone of your intended route, and the expected time of return.