source image courtesy of Eat & Sip in the City
1. This might sound obvious, but it is important: remove window air conditioning units.
2. Install thick curtains.
3. Use draft stoppers under leaky doors.
4. Open shades on sunny days, close shades at night.
5. Reverse your ceiling fan rotation to send trapped head downwards.
6. Dress warmly - you shouldn't feel comfortable in shorts in the dead of winter!
7. Install plastic window insulation film.