Drafts from your windows and doors can account for 25% of the heat loss in your home. You can use a rubber seal on your windows or doors to fill gaps of 3-5mm. Tear the rubber seal in half and remove the adhesive strip. Stick it onto the inside edge of the door stop, starting at the very bottom, and then work your way up to the top and straight across.
Door seals work by pushing the flap down when the door shuts, keeping the wind and the rain out. There are many different sorts of storm seals and adhesives. Make sure you choose the right one for your type of door.
Hardwood floors and tiles look great but can get very cold. In particular, hardwood floors often have gaps that let in drafts. It's a good idea to lay down thick rugs on these types of floors. They feel great underfoot and stop the winter chills.
Make sure your windows are well sealed. Check that the external and internal seals are in good condition and push hard against each other when the window is closed. Closing your blinds and having good quality block-out curtains can reduce heat loss by 10% in your room.
If you have a ceiling fan there's usually a reverse mode for winter. This will push all the warmer air down, making the room temperature more comfortable.
You can also insulate your roof. Installing insulation batts above your ceiling will help keep your home warm in winter and also cool in summer. However, it's important to consider the type of insulation that will best suit your home.