Toddler speech: Common problems and normal development

Listen to toddlers speaking often enough and you'll hear the same mistakes over and over again. This can be oddly reassuring to a parent, hear another child refer to a cat as dat or a rabbit as wabbit and you can mentally tick off the 'normal speech development' box.
What is interesting though is that while one of those mispronunciations (wabbit) is part of normal speech development the other (dat) is not but rather a common error. Normal speech development will result in some mispronounciations as children learn where they need to place their tongues to make the correct sound. In contrast, common errors in speech development occur as a child has had a disruption in the development of speech when that sound may be acquired. Since the reasons for this disruption are things that commonly occur to all children such as colds, ear infections or even just being focused on another element of their development when that skill should have been developing, most children will possess some of these errors. In fact, these errors are so common that most information for parents will barely acknowledge them as errors but instead will simply tell you the age at which they will outgrow them.

Age by which 75% of children used the speech sound listed accurately. Speech sounds The manner in which the speech sounds are produced. 3 years h as in he zh as in measure y as in yes   w as in we ng as in sing m as in me n as in no p as in up k as in car t  as in to b as in be g as in go d as in do Voiceless fricative Voiced fricative Voiced glide Voiced glide Voiced nasal Voiced nasal Voiced nasal Voiceless stop Voiceless stop Voiceless stop Voiced stop Voiced stop Voiced stop 3 years 6 months f as in if Voiceless fricative 4 years l as in lay sh as in she ch as in chew Voiced liquid Voiceless fricative Voiceless affricate 4 years 6 months j as in jaw s as in so z as in is Voiced affricate Voiceless fricative Voiced fricative 5 years r as in red Voiced liquid 6 years v as in Vegemite Voiced fricative 8 years th as in this Voiced fricative 8 years 6 months th as in thing Voiceless fricative

From here
This is fine if your child is confident and happy and the mispronunciation does not get in the way of their generally being understood. However for some children not being understood can be frustrating and upsetting leading to either tantrums or an exacerbation of shyness.
For these children, the fact that these errors are common does nothing to reduce the frustration that they feel.

What can you do about it
First of all, pay attention. Notice the sounds he/she has problems with, where they are located in the word and the consistency of the mispronunciation. A sound that is pronounced correctly some of the time is likely in the process of correcting itself and will need minimal help to correct.
Secondly, repeat the sound back to them correctly but without obviously correcting the child. For example, child: 'look dat' Parent: 'What a big cat!, where did that cat go?'. You should slightly emphasise the sound you want them to notice.
You can also engage in some rudimentary speech therapy exercises with them. For toddlers, it is important that you are just having fun playing with the sounds and it does not become too chore like for them.  Good activities for younger children are:
              Auditory bombardment: Repeating the sound while playing with the child e.g. while playing with a toy cat - cat goes in the car, cat kicks the can for 5 to ten minute bursts spread out over the day
                                                 Pointing out things in books with them that have that sound
                                                 Putting out toys and activities that allow you to use the sound, so if your child is having trouble with t it may be a good time to bring out the trucks, trains and teddies.
              Getting the child to repeat the sound back to you as part of a game e.g. blow bubbles and the child has to say pop, pop, pop as they pop them.