Caroline Bowen's article on The Butterfly Procedure for lateral /s/ and /z/ (in 10 easy steps).
Show proper placement and production on internet sites such as:
Description of how to produce the /s/ sound: The correct production is made with the teeth nearly closed in a natural bite position and the lips parted as though smiling. The sides of the tongue are raised against the upper side teeth. The tip of the tongue may vary as to the position but is usually raise to approximate a place behind the upper front teeth. The tongue should form a groove down the center, through which the breath is directed in a continuous stream. (a mirror is beneficial).
For frontal or interdental lisp, instruct the individual to "Close your teeth and say /s/."
Have the child watch you make the /s/ sound and have him watch himself in the mirrors while you are still doing it with them.
When a cat is mad it may hiss. Can you hiss?
Have them practice voiceless "th" sound then have them place tongue behind front upper teeth. Slide from voiceless "th" sound to /s/.
Have the child protrude the tongue between the teeth so as to produce the voiceless "th" sound. Have him think of the voiceless "th" sound. When he is thinking of producing the voiceless "th" sound for the /s/, force the tip of his tongue inward with a thin instrument such as a thick blunt toothpick. The result will be an /s/. The principle involved is that the child's thinking the voiceless "th" sound, drives the air over the tip of the tongue. The value of directing the child's attention to the tip of his tongue when he is producing sibilant sounds is that he will eventually feel the current of air being emitted over it.
This time say [i]: Do you feel the position of your tongue touching the upper teeth and gums at the back? Now as you say /i/ raise the tip of your tongue up to the ridge directly behind your front teeth and gently below. Did you hear the /s/ sound?
Have the child begin by forming a /t/ in a word like tea. Have him pronounce it with a strong aspiration (tuh-hee), with a strong puff of breath after the explosion of the /t/, before the vowel begins. Then, instead of this sudden explosion or puff, take away the tip of the tongue from the teeth ridge slowly. This will give the sounds. Hold onto this sound and you will have the s-s-s-s. The child must not think he is saying ts as in the word oats or he will use his usual pronunciation. Keep him rehearsing the steps until they are fixed.
Make a /S/ (sh) sound with pursed lips. Next, change your lips to a smile, and change the sound to an /s/. Do consecutively.
For the /s/, pair words can be used for the purpose of demonstrating essential differences between sounds that may be confused. Distinguish between the voiceless "th" sound and /s/ in minimal pairs such as the following:
Have the child hiss, seeking to raise the pitch of the hiss until it approximates that held by the instructor. Often it is wise to tell the student to experiment with the tongue tip positions during the production of hiss hiss, not before. Sometimes the instructor should change his hiss from the faculty one used by the student through several degrees until the corrects is made.
Instruct the childs to put upper and lower teeth together. Using his tongue, ask him to stroke the back of his upper teeth as he blows a stream of air.
A child with a lateral lisp you may want to suggest that they position their tongue tip behind their lower teeth to produce the /s/ sound, rather then behind the upper teeth.
Use a straw as a resonating tube, demonstrate that lateral /s/ us made is resonates on the side of the mouth and when the good sound is made it resonates in front of the mouth. The straw can be used temporarily to reinforce correct production of the /s/.
Donna Ridley - developed a system of correction of a lateral lisp /s/ distortion by means of an invented foreign language and correction of a lateral lisp by changing it to a frontal lisp; http://home.earthlink.net/~donna.ridley.slp/id1.html
From discussion about lateral lisp on the MSHA mailing list
Paul A. Dagenais, Paula Critz-Crosby, and June B. Adams Defining and Remediating Persistent Lateral Lisps in Children Using Electropalatography: Preliminary Findings Am J Speech Lang Pathol, Sep 1994; 3: 67 - 76.
Hoch, L., Golding-Kushner, K., Slegel-Sadewltz, V. L., &Shprlnt..J. B.(1975). Case study: Therapy procedures for remediation of a nasal lisp. Journal of Speech and Heanng Research Language, Speech, and Hearing Services in Schools, 6,29-32.
Dennis M. Ruscello, Linda I. Shuster, and Annette Sandwisch Modification of Context-Specific Nasal Emission J Speech Hear Res, Feb 1991; 34: 27 - 32.
Bruce P. Ryan, A Study of the Effectiveness of the S-Pack Program in the Elimination of Frontal Lisping Behavior in Third-Grade Children J Speech Hear Disord, Aug 1971; 36: 390 - 396.
Carol E. Schlip The Use of Cued Speech to Correct Misarticulation of /s/ and /z/ Sounds in an 8-Year-Old Boy with Normal Hearing Lang Speech Hear Serv Sch, Oct 1986; 17: 270 - 275.