The shoes and socks that you wear whilst walking are very important - blisters will make an enjoyable walk a miserable affair.
Make sure that your socks fit well and are not too worn. Avoid tube socks as they will not fit well. Avoid socks with bulky stitching at the toe or heel or made from materials such as cotton which absorb moisture. Always make sure your socks are clean. If going on a long walk, wear socks that you know do not give you blisters and consider taking a spare pair of socks with you. Some people find wearing two pairs of socks prevents blisters.
The shoes you wear should be comfortable, fit well with plenty of toe room and have a flexible sole. Good walking boots protect your feet keeping them warm and dry, provide a good grip and also protect your ankles. Walking shoes are a light alternative to boots but they offer no real protection to your ankles. Walking sandals are suitable for summer walking but give no protection to your feet from undergrowth or support for your ankles. You can also use good quality trainers but they are unlikely to be waterproof.
Go shopping for shoes in the afternoon after a walk as your feet expand during the day. Wear the socks that you would normally wear when walking. Make sure you buy proper walking boots rather than high street fashion boots that look like walking boots but do not give the protection and comfort required. When laced, your heel should not move, your feet should not feel pinched and you should be able to move your toes freely. Take your time to find a pair of shoes that fits properly. Try wearing new shoes round the house for a few days before using them on a walk - the shop may still allow you to return them if they do not fit properly.