Start the conversation normal... you know, hey, how's it going etc etc. Then, as the conversation goes on, tease her a bit, make some jokes, etc. Same as you would do if you were flirting with her in person. Then make some sexual innuendos and see how she responds. After that, just use your imagination! Have fun!
seducing a girl thru text messages just like talking dirty. You have to have a good imagination and descriptive too. Also the girl have to want it to. It is fun to do with the girl that have feeling for you. Then she wouldn't look at you as a psycho. Good luck!