My wife is a speech and language therapist for under 5s and we have 2 children under 5 ourselves. There are so many techniques she uses without even thinking about it to encourage communication that, left on my own, I would never have known to use. For example, in the really early days, when a child said "blah blah blah blah" I would have been inclined to repeat it, but now I'll say "that's right, an aeroplane!" (Or whatever it is).

Parent-child interaction goes a really long way in child development and if you ever get the chance, it's worth sitting in on a session (whether your child needs extra help or not). A large part of the work my wife does is around enabling parents to assist kids that need more input (through no fault of the parents themselves).