This video explains the difference between frontal and lateral lisp.  Pam Marshalla is a veteran SLP who is a leader in the treatment of motor speech disorders.  

Pam Marshalla is a veteran SLP with strong emphasis on motor speech disorders.  These vowels placement cues are so helpful for students with Apraxia of speech and phonological errors when speaking.

ASHA.org is the webpage for our national organization which houses a wealth of information for parents and educators.