The important thing with predictive text is that you hit the letter key ONCE for each letter.
Suppose you want to type RUN.
So on the PQRS key, if you want R you press the key once (this can be P or Q or R or S)
Next you want U so you press the TUV key ONCE (so second letter can be T or U or V)
Now you want N, so you press the MNO key ONCE (so third letter can be M or N or O)
So the phone knows you want to start the word with P,Q,R or S, next you want T,U or V, finally you want M,N or O).
The phone looks up its list of common words that have these letters in them and offer RUN.
And you do the same for each word. If the word it offers is wrong you step on to the next word.