Drafts make us feel cold.
Stopping or minimizing drafts will help to keep your home feeling warm. Windows and doors are a major source of drafts. Make sure your weather stripping and caulking is in good repair around your doors and windows. The door sweep usually wears out first and is easily replaced.
Another spot for eliminating drafts is the header joists at the top of the foundation. This area should have insulation. Spray foam around any pipe penetrations to seal up prior to installing some insulation. For larger gaps, you can stuff a bit of steel wool in first to deter animals from chewing through foam to get inside. To finish, caulk the outside of all pipe penetrations.