Feet are the most important part of a walker's anatomy, so look after them.
If you want to walk in all kinds of weather; especially extensive walks out in the countryside, you should invest in some footwear designed particularly for walking.
Walking boots with sturdy moulded soles are the best solution, as they protect the feet and keep them warm and dry, and also provide grip and support for the ankles, which is a serious requirement for taking on steep hills and slopes.
Walking shoes are a lighter option, offering a tough protective sole with reasonable grip, but have no ankle support.
Trainers are not recommended as they are not waterproof and give very limited support and protection.
An extensive range of walking boots is available both at physical stores and online. There are weighty, robust boots for rugged conditions, and lighter boots for summer walking. Although traditional leather uppers stay popular, lighter, "breathable" waterproof materials are also used in manufacture. Boots are also available to suit different types of feet, in both narrow and wide sizes; in men's and women's fittings, and you can even get boots made to measure, but that of course comes at a price!
What you choose will depend upon when and where you want to walk, your budget and your personal preferences, and the perfect boot for one walker will rarely suit another, so it's worth taking time to find out and shop around.
When selecting your footwear, look for proper walking boots from a good outdoor shop: beware of high street 'fashion label' boots that look like walking boots but will not give you the comfort or protection you need.
Walking boots are best worn with thick socks so wear your normal walking socks when trying them on, or ask the shop to lend you a pair and then you can take your time choosing. Ask for advice, and above all else make sure the boot feels really comfortable when laced up. The boot should hold firm around your entire foot without feeling too cramped; your heel should not move around, and your big toe should not be pressing against the upper part of the boot.
Never buy secondhand walking boots - they will have been 'run in' on someone else's feet which precludes the ability for the boots to mould themselves to your particular anatomy. Buying walking boots is an important first step in taking up the hobby - make sure you get it right from the start!