To use predictive text input by default when writing text in English, select Settings > Phone > Language > Predictive text > On.
Write the desired word by tapping the relevant keys only once for each character. The word suggestion changes each time you tap a key.
If the word is correct, tap 0 to add a space and continue writing.
If the word is not correct, tap * repeatedly to display the words that match your writing.
A "?" character after the word indicates that the word is not in the dictionary.