Usually a woman would receive цветы́ (flowers) and a box of her favorite chocolates or candy from her boyfriend or husband, and maybe a small romantic gift on Valentine's Day. Романти́ческий у́жин (romantic dinner) is also very popular in Russia on Valentine's Day, whether it's a homemade candlelit dinner or a dinner at a fancy restaurant.
Another popular пода́рок (gift) is a Valentine's Day card with a romantic message inside.
This is how to wish Happy Valentine's Day in Russian:
С Днём Свято́го Валенти́на!