In America, on Valentine's Day, men are expected to give cards, candy, flowers, or jewelry to their sweetheart.  Women may also give a card or a gift, but usually the bigger gifts are given by the guys. The couple might go out for a romantic candlelight dinner.  

For Valentine's Day in Japan, by contrast, girls give the gifts (especially chocolates) to their lover or someone they have a crush on.  It looks like the Japanese follow the way of Valentine, who sent a letter to the daughter of his jailor just before he died (see the brief history below).

(2)  A very Brief History

The origin of Valentine's Day traditions is unclear.  Some believe that it is derived from an ancient Roman fertility festival held on February 15.  Others believe that Saint Valentine himself was the origin of some of the traditions.  One legend says that, while imprisoned, Valentine fell in love with the daughter of his jailor, and just before he died, he sent a love letter to the daughter.  He signed the letter, "From your Valentine."  This supposedly is the origin of Valentine's Day cards and letters. In any case, February 14 was established as Valentine's Day by the Pope around A.D. 498.

Source:  < http://www.historychannel.com/exhibits/valentine/ >

Note: (1) An interesting example of special events on Valentine's Day： The Como Conservatory in Como Park , St. Paul will host Valentine’s Day Soiree on February 14^th from 6:30 through 11:00 p.m.  You can enjoy candle-lit gardens, camellias’ scent and romantic music.  Our photos on the Como Conservatory 

Source < http://www.ci.stpaul.mn.us/depts/parks/comopark/czcs/calendar.html >    

(2) Dining at the Twin Cities < http://www.twincities.com/mld/twincities/entertainment/dining/5114497.htm  > Sites