The seventh and final group of consonants -- श, ष, स, ह -- is the fricative consonants ( Fricative consonants). As an aerospace engineer, fricatives are easy for me to understand. Fricatives are formed by forcing the air from your lungs into a tight channel and causing turbulence in the air flow; it's like placing a model in a wind tunnel.

श
śa, /ɕ,ʃ/

ष
ṣa, /ʂ/

श and ष are essentially two flavors of sh. श (śa) is a palatal consonant, so it should be articulated with the top of the tongue against the palate. ष (ṣa) is a cerebral consonant, so it should be articulated with the tip of the tongue placed against the palate, behind the location where श is articulated. So, for me, an American, it is a matter of getting the tongue placement right.

स
sa, /s/

ह
ha, /h,ɦ/

स and ह are just like their English transliterated counterparts, sa and ha. They are very common letters, as well. The alphabetical order of the first five groups of consonants followed rows in the table below. However, the alphabetical order of the sixth and seventh groups follows the columns. Thus, the alphabetical order is: (labials) प, फ, ब, भ, म; (approximants) य, र, ल, व; (fricatives) श, ष, स, ह.

I am archiving this information about the alphabet on the Hindi page: kirkkittell.com/language/hindi. More information from Wikipedia:

• Approximant consonants
• Sounds represented within /.../, e.g., /k/, are symbols of the International Phonetic Alphabet (IPA), which is extremely useful for me to understand how Hindi sounds.
• Sounds such as ka are transliterations from the International Alphabet of Sanskrit Transliteration (IAST). It's simpler to understand than IPA.