Being coy and cute can help to win the attraction of the subject of your flirting. Utilize smiley faces, offered as icons on some instant messaging boxes or phones, or created manually by combining a colon with a right parenthesis. Use the smiley faces wisely and don't overdo it, as this could become overbearing and annoying. For example, if you are suggesting that the object of your flirting come out for a drink, add a winking smiley face at the end of the suggestion to hint at something more. A winking smiley face is made with a semicolon and right facing parenthesis.
Utilize puns and word plays to your advantage. This is effective for making obvious hints that will pique the recipient's interest. For example, suggest that he come to a house party where there will be a volleyball net set up. Follow this suggestion with "we could play." In the literal sense this would relate to the game of volleyball, however the recipient will wonder if you are talking about something more intimate. The casualness and distance involved with text and instant messages allows you to make subtle word plays that are open for interpretation, ideal for flirting.
The time delays in messaging allow you to make bolder comments and statements because you have more time to craft your responses. Since the recipient cannot see you, you could have easily wandered away from the computer or phone for several minutes. This is the motivation needed for making more overt and obvious suggestions that you may be too shy to make in person. The lack of physical contact and the delay between messages can help you make a suggestion, then backpedal from it if it then seems to forward. Backpedaling could also be another coy form of flirting. For example, if you tell him that you thought he looked attractive the other night, after he responds you could joke and say that you posted the comment on the wrong message box, with a smiley face following it.