Phonological developement of children's pronounciation

Infants often make sounds and noises which are not part of the language that they are hearing. Whilst growing up, within the first 6 months of their life a lot of their mis-pronunciation is due to psychological factors, such as the positioning of their jaw and tongues.
-Vowels are achieved before consonants
- By the age of 2 and a half, the average child has mastered all the vowels and around two thirds of the consonants.
-Consonants are first used correctly and the beginning of words, but consonants at the end of words are more difficult, for example "p" and "b" sounds in "push" and "bush" will be easier to pronounce than "rip" and "rib".

Deletion
Children will very often delete certain sounds/letters from words in order to simplify it for them. For example, banana becomes "nana" and final consonants are sometimes also deleted, so hat becomes "ha" and cat becomes "ca".
Sometimes quite often, a child can have a phonological delay, this occurs when -
The child finds the patterns/sounds from the English language really confusing, therefore finds it difficult to pick up and repeat.
The child has poor perception and doesn't have very good awareness of how their speech sounds and why other people fail to understand what they are saying.
A phonological delay can be identified through these things -
If your child is missing out initial sounds in their words, so referring to their bed as "ed" etc.
If they are deleting the ends of their words.
-Also, if your child cannot pronounce numerous vowel sounds.

https://www.york.ac.uk/media/languageandlinguistics/documents/staff/publications/Velleman&Vihman%20ch%202.pdf
http://revisionworld.com/a2-level-level-revision/english-language/child-language-acquisition/phonological-development
http://www.playingwithwords365.com/2011/09/phonological-processes-and-phonological-delay/