Pores are tiny hair follicles in the skin. They may take on a larger appearance when they are clogged with dirt or oil.
Its always important that pores are clean and smaller and this can be achieved by making sure to keep them clear.
During the day, use non-comedogenic moisturisers and makeup (they don't block pores and are usually water based products), and avoid products that contain heavy ingredients, like petrolatum/Vaseline, as this irritates the pores and make them look bigger.
There are several tricks to minimising pores, this is one you should try. Watch it above.