Flirting can be an actual game. Let your boyfriend guess what color panties you are wearing, and offer a prize -- it doesn't have to be expensive -- if he guesses correctly on the first or second try. Or choose something special -- a hotel room for the night or tickets to his favorite sporting event -- and leave him hints. When he guesses correctly, present them to him.

Send your boyfriend a flirty text message in the middle of the work day, or while he's hanging out with his friends. You may put a smile on his face with a message that reads, "You are the sexiest man in the whole wide world," especially if he's having a stressful or busy work day. Don't overdo. One or two a day is more than enough.

Love letters -- handwritten and mailed -- spice things up. There is no right or wrong way to write a love letter, notes "Huffington Post" writer Himay Zepeda. Think about what you really want to say about your relationship or about him specifically, and commit it to paper. You can remind your boyfriend of his best qualities or include romantic gestures you would like to do to him when you see him next, like wildly kissing him the moment he walks in the door or giving him a sensual massage. Go the extra mile and purchase special stationery.

There are all sorts of games the two of you could play, including Truth or Dare or naked Twister. Make up your own game based on interests that the two of you share, such as acting out romance scenes from your favorite movies. Have a playful pillow fight and end it with some pillow talk.