A reliable decision about stopping starts with the word's final written form, then the underlying vowel, and then any cause involving madd or tanwin. The following examples illustrate distinct rules.
«أَنَا»: a written alif with different joining and stopping treatment.
«نَسْتَعِينُ»: an originally dammah-ending nun allowing ordinary iskan and, where correct, rawm or ishmam.
«الْعَالَمِينَ»: a final kasrah that may permit rawm but not ishmam.
«رَحْمَةٌ»: ta marbuta becoming a still ha in stopping.
«عَلِيمًا»: fathah tanwin replaced by the alif-length sound at an ordinary stop.
Their endings are not identical, so “just make the letter still” does not fully classify every case. Sound analysis combines spelling, underlying vowel and the special stopping form.