A primary place where cold air can enters the house is where siding meets the foundation. A quick remedy is to caulk the space in between. It is also a good idea to fill and seal all exterior areas where different materials meet, such as where flashing abuts concrete.
A good choice for this application is a latex-based caulk that can adhere well to concrete and masonry. There are latex-based sealants that are impregnated with silicone for extra water resistance, durability, and adhesion. A polyurethane sealant designed for concrete and masonry can also do the job. Both types are paintable.
For larger gaps or cracks, you may wish to use a latex-based insulating foam sealant. The foam expands into the area to be sealed, providing an effective barrier against drafts and pests. This type of sealant can also be painted once it has set. You can buy insulating caulk online.