I copy this from another answer on here...
In the "Write messages" screen, press "#" several times and watch the symbol in the top right change. If the pencil has 'speed lines' behind it, then predictive text is enabled. If there isn't the lines behind the pencil, then predictive text is turned off.
There are several modes of text entry:
1) Predictive Capitalised First Letter (Lines > Pencil > Abc)
2) Predictive Capitalised (Lines > Pencil > ABC)
3) Predictive Lowercase (Lines > Pencil > abc)
4) Non-Predictive Capitalised First Letter (Pencil > Abc)
5) Non-Predictive Lowercase (Pencil > abc)
6) Non-Predictive Capitalised (Pencil > ABC)
You can scroll through these modes using the hash key (#) as described before. The "#" key is the bottom right key on your mobile phone's keypad.
Copy Cat, April 2009