It is just your words, and your timing. Follow these flirting tips for texting to get optimum results.

Flirting Tips for Texting No. 1
Firstly you need to make sure that the subject is free for flirting. While in person, you would make the attempt to actually attract a person's attention physically, here, you need to make sure that the person will be paying attention to your flirty text messages. So, it is always safe to ask him/her "hi. How is your day going?" or something along these lines. Another option is to send them a message at the same time everyday. Like, as a routine send them a good morning (non flirty) message every morning. Very soon, they will get used to it, and you will have their attention.

Flirting Tips for Texting No. 2
Do not message very late at night. Primarily, people may not appreciate it due to the fact that their sleep will get disturbed. Secondarily, it is highly inappropriate to sms an individual late at night. Especially, when the nature of the sms in flirtatious. Unless you hear it from their mouth, that it is OK for you to sms them at night, refrain from doing so.

Flirting Tips for Texting No. 3
Refrain from using too many abbreviations for texting. This is because, the recipient may not be completely aware of all the abbreviations. In such a case, if you end up using an abbreviation that they do not understand, the cause will be lost. In fact, many people really appreciate people using normal spellings in sms. However you can used the general shortcuts like
These sms shortcuts are used often and by most people.

Flirting Tips for Texting No. 4
If you do not receive a reply to 3 text messages in succession, don't sms further. This is because, clearly your messages are not making a difference to the receiver. Another possibility could be that the receiver is busy. In such a case, it is best to let them be. They will call you back when they get free.

Flirting Tips for Texting No. 5
Proofread the sms before you send it. Trust me, the amount of mistakes made while typing an sms, and the difference in perception that it may cause can be detrimental for the "relationship".

Flirting Tips for Texting No. 6
Be suggestive in what you say. Don't just come out and say things. Be a little bit indirect. Create buffer. This way if you keep a buffer and lead into flirting gradually, the receiver won't even realize that you're flirting. You will just seem very cute and the flirting will seem natural.

Flirting Tips for Texting No. 7
Use emoticons or text messaging symbols. I hope you know what they mean. They are the tiny icons to show a smiley face, or a crying face. This way you both will be sharing smiles in good times and tears in tough ones.

Flirting Tips for Texting No. 8
Never send the same text message to two best friends together. Especially when they are together. This will not only make them want you more, but their rivalry will get more attention. The best thing to do is find really random but normal text message. This way they will stay in touch, and you will seem friendly.

Flirting Tips for Texting No. 9
Since two people cannot look into each others eyes via sms, you will need to describe whatever you are feeling. While it may seem tough at start, you just need to open up. Let her know how you are yearning for her touch, or how you really want to feel her skin. Just open up and describe all that you feel.

Flirting Tips for Texting No. 10
Be prompt in replying. This is the last but not the least important tip for flirting via sms. If you are trying to flirt with someone via sms, playing hard to get is not the safest option. Reply promptly. Especially if the two of you are having a night time conversation. Since you started the flirting, you will have to be there the whole time. Do not leave them waiting for a response. For all you know, they may fall asleep during the wait. Not a very good sign, right? So be prompt, but not obsessive.