PLAN your walk carefully and carry a MAP and compass as well as your phone.
If possible, walk in pairs or small groups.
Check the WEATHER forecast and remember that the weather can change quickly particularly in winter.
Wear suitable CLOTHING and, in particular, boots appropriate for hill walking.
Carry FOOD & DRINK and additional warm and waterproof clothing (including hat and gloves). If you have to stop walking, you will cool quickly.
TELL SOMEONE where you are going and when you expect to be back.
Carry a FIRST AID KIT including a survival bag that will keep you warm in an emergency.
Remember that mobile phones may not have a signal in the hills so do not rely on them for making contact or route finding. They can also fail in extreme cold.