A sense of humor is usually at the top of the list of things people look for in a potential mate and is definitely something that should be part of your online flirting repertoire. Teasing can be a great way to incorporate humor, but be careful that the tone is kept light and playful so it is not misinterpreted. A safe option might be to poke fun at yourself or base jokes around objects instead of people so you can show off your humor without being unintentionally insulting.
Too many people get too caught up in what they want to say next without paying attention to what the other person is doing or saying. Being observant and taking a genuine interest in the person will go a long way to make sure your online flirting comes across as sweet and caring instead of superficial of shallow.
Because of the anonymous and private nature of the Internet, people can be far less inhibited when talking online than they would be in person. This can be a good thing, especially for shy or self-conscious individuals, but it also can have some drawbacks. One is the potential for innocent flirting to quickly escalate into a sexually explicit conversation. A flirtatious remark that is a little too sexy might encourage the other person to take the conversation "to the next level" and make you feel uncomfortable, or can make the other person uncomfortable and ditch the conversation altogether. It is perfectly acceptable to let the other person know you are attracted but it might be best to save sexy remarks for when meeting in person.
Many times, online flirting takes place between people who don't know each other. When that's the case, it's important not to reveal too much personal information. Remember, you might not know as much as you think you do about the person on the other end of the computer connection. The anonymity of the Internet can breed lies and deception, and you do not want to inadvertently involve yourself with dangerous individuals. Use caution whenever giving any personal information--particularly identifying information like your address, city, phone number, last name or place of employment--until you can prove the identity and intentions of the other person.