1. Use Layers of Clothing
The best way of regulating your core temperature is by using layers of clothing. At the most basic level, the layering system consists of three different layers. Each layer serves its own purpose. These layers include a base layer, mid-layer, and outer layer.

a) Base Layer – the base layer works by keeping your skin warm and dry. It also helps by wicking away moisture from the skin as it develops. This layer usually consists of a semi-snug-fitting shirt such as an Under Armour type shirt or a Nike Dry Fit shirt.
b) Mid Layer – the mid-layer is used to keep the warmth that your body naturally generates. This can be a fleece jacket or a soft-shell jacket. Depending on the weather outside, this layer can be thicker or thinner.
c) Outer Layer – the outer layer protects you from wind, cold, or sometimes rain. On Kilimanjaro, you will need to bring a full complement of rain gear – including a rain jacket and rain pants. Also, a warm down or synthetic jacket is essential. Lastly, clients should opt for a pair of gaiters and also get a rain cover for their day pack.

2. Protect Your Head and Face
Protect your head from wind, sun, and cold by wearing something on your head at all times while trekking. This can be a cap or wide-brimmed hat when it is warm, or a knit hat when it is cold. You may also want to get a balaclava or a scarf for your face to shield you from wind and dust.

3. Keep Your Extremities Warm
Your hands and feet happen to be one of the hardest parts of your body to keep warm, as the human body decreases the blood supply to your extremities when the body as a whole is cold. Climbers should bring warm, waterproof gloves and boots.

See more here: https://www.youtube.com/watch?v=HV3J_j8anuM