Age 12 to 18 months:

• at 12 months, does not use gestures such as waving or shaking head

• by 12 months, is not practicing using a couple of different consonants

• by 12 months, is not somehow communicating to you when
  needs help

• at 15 months, does not understand and respond to NO

• at 15 months, cannot say at least 1 to 3 words

• at 18 months, is not saying at least 6 to 10 words

Age 19 to 24 months:

• by 19 to 20 months, is not pointing out things of interest,
  such as bird overhead

• by 20 months, is not producing at least 6 different consonant
  sounds

• at 21 months, does not pretend play (brushing doll’s hair)

• by 24 months, does not imitate action or words of others

• by 24 months, cannot point to named pictures in book

• at 24 months, cannot join 2 words

• at 24 months, does not know the function of common
  household objects

Age 25 to 36 months:

• at 26 months, uses no 2 word simple sentences

• at 30 months, cannot name at least 3 body parts on self

• by 32 months, has difficulty singing fragments of nursery
  rhymes

• at 36 months, does not ask questions

• at 36 months, cannot be understood by strangers at least
  half the time

• at 36 months, is unable to articulate initial consonants
  (says all for ball)

• by 36 months, is unable to name most common household
  objects

Age 3 to 4 years:

• at 3, cannot speak in short phrases

• by 3, is unable to understand short instructions

• at 3, has no interest in interacting with other children

• at 3, has extreme difficulty separating from a parent

• by 3 ½ , consistently fails to add the final consonant to
  words

• at 4, still stutters frequently, often accompanied by facial
  grimacing

• at 4, is not fully understandable

(Speech & Language Development Chart, 2nd ed., A. Gard, L. Gilman, J. Gorman)

1. Read, Read and Read more to your child

2. Look at your child when you speak

3. Listen to what your child has to stay

4. Take child grocery shopping & identify different foods.

5. Talk about the color and shape of everything

6. Use spatial and directional words (under, above, in, etc.)

7. Compare objects

8. Discuss the function of an object (what an iron does)

9. Ask child questions and listen for the correct answer

10. Use descriptive words (long, curly, short, tall)

11. Understand time (day, night)

12. Quantity (whole, half, all)

13. Count out loud

14. Allow child to help with cooking and discuss steps

15. Use prepositions

16. Say a short sentence and encourage child to repeat

17. While putting together a puzzle, take turns and name the picture on the puzzle

18. Imaginary play

19. Acting out

20. Speak clearly to child

Basically, the most important thing you do with your child to enhance their speech and language skills would be to talk to your child, listen to your child, and interact with your child.  The child learns from his caregiver.