Start off a sentence and encourage your child to finish it.
For example. “Katie, you want a…….” whilst holding a drink for the child.
To begin with, your child may not finish the sentence and you may need to complete it for them after a pause.
In time, your child will get to know what is expected and will fill in the gap.
This technique can also be used to talk about what your child is doing. For example, when playing with the trains you could say something like “Jamie's playing with the (pause)….. train” The train goes …. Choo choo”