Carry a map and compass and know how to use them. Choose appropriate footwear for the terrain. Solid, lightweight walking boots are best. Sandals can be used on tracks in summer and around your campsite. Dress in layers and always carry a jacket.
Weather conditions can change unexpectedly.
Use poly-pro or fleece clothing. Cotton traps moisture. Carry water and emergency supplies even on short hikes. Repackage snacks and food in baggies. This reduces weight and the amount of trash to carry out.