There are the usual ways that we know to keep our bodies warm this winter. The most common is increasing the environment’s temperature. Let us use a bit of science to add more heat to our bodies and to harness heat from the environment.
Wear rain gear

For starters, yeah, far off. Fewer pores on our clothing, less heat escape. Keeping yourself warm means not letting your generated body heat dissipate to the environment. Keep it for your self.
Hot packs
Say, you are going out of the house for a short time. Put a small hot pack on the insides of your coat. This would keep your internals warmer.
Keep your hands warm

From a military research documentary; blood passes through your hands as it cycles through your body. Having a steady heat applied to the hands will warm the circulating blood.
Clumping together
We want to share our body heat with someone else and not the environment nor to our clothing. In contrast to the earlier tip; wear less so that the person next to you can feel your body heat.
Clump and cover yourselves in a less-porous blanket. This will cycle the heat internally, within the blanket.
Eat more fat

Animals in cold regions rely on their body fat to keep them warm. Remember, humans and animals of the same kingdom. If you see that cold days are coming, stack-up and eat a lot months before. Remember, gain fat, not muscle.
Store energy
Eat more carbohydrates than your body can burn, turning them into fat.
More caffeine (not necessarily hot)

While it is obvious that the hot water that we added to our coffee warms your body, it is not what we are after. Caffeine stimulates the release of fatty acids. Coffee and bacon would be a great pair.
Sit near your fridge after a stack
Your fridge had to get the heat out of the food to cool the insides. Therefore, the more food, the more heat it has to give out. It is a nice spot to be during cold days.
Let more sunlight in

There is what they call radiant heat; an exchange of energy by photons. Energy equals heat. Just a reflection of the sun’s light will add more heat to the environment.
Turn those appliances on
Put our hands at the back of your TV and monitor. You will feel a significant amount of heat. The more these running, the more heat is dispersed to the environment. However, sorry about the electricity bill.
Turn on your mobile data.
If you are will keep your phone in the inside pocket, make sure that the mobile data is on. Your phone will be hotter.
Use halogen instead of LED

Halogen emits 20% light and 80% heat while LED emits 80% light and 20% heat.
Turn on ceiling that fan
Hot air rises. The ceiling fan will push down the warmer air.
Let us now apply some the science.
Clump beside the fridge, under a halogen light. Two or three persons wearing regular clothing. Cover yourselves in a less-porous blanket. You might want to put a hot pack on the inside of that blanket. Make sure that all of you are well fed. A sip hot coffee from time to time would be nice.
Isn’t that warm?