IKHFA:

If any of these 15 letters ت,ث,ج,د,ذ,ز,س,ش,ص,ض,ط,ظ,ف,ق,كappears after a نْ (noon saakin) or ــًــــٍـــــٌـ (tanween) it will be
pronounced with a light nasal sound (gunnah) for a duration of two harkaats (2-3 seconds duration)

IKHFA MEEM SAAKIN:

When the letter ب appears after a مْ it will be pronounced with a light nasal sound (gunnah)

QALQALA:

The five letters of Qalqala are ق,ط,ج,ب,د ,When any of these letters in a word has a Sukoon on it or if deciding on pausing on any of these letters which appear at the end of a sentence it will appear to have an echoing or jerking sound.

IQLAB (QALB):

If the letter ب appears after a نْ (noon saakin) or ــًــــٍـــــٌـ (tanween) then the Noon Saakin or Tanween will be incorporated into the letter م (small meem) and will be recited with Ghunna.

GUNNAH:

نّ & مّ Both of these words are pronounced with a nasal sound

IDGHAAM:

If any of these letters ي,ن,و,مappears after نْ (noon saakin) or ــًــــٍـــــٌـ (tanween) it will merge into the letter and will be recited with nasal sound (gunnah)

IDGHAAM MEEM SAAKIN :

If after a مْ (meen saakin) there appears another مّ (meem) the two meems will merge and will be recited with nasal sound (gunnah)

Please note:

Sometimes the letter مّ appears with نْ (noon saakin) or ــًــــٍـــــٌـ (tanween), for example اُنَاسٍ مَّشَرَبَهُمْ here GUNNAH and IDGHAAM both the rule of tajweed
will be applied, but the style to read both the tajweed
are the same i.e. with nasal sound (gunnah)