What it does
Darga is a conjunctive trope, almost always the lead-in to Tevir. The pair Darga-Tevir is a standard sequence, parallel to how Munach leads into Etnachta and Mahpach leads into Pashta.
Where it appears
Common throughout the Torah. Look for Darga one or two words before a Tevir. It's less universal than Munach but tightly coupled to Tevir whenever Tevir appears.
How to remember it
Darga means "step" or "staircase." The mark below the letter zigzags like steps going down. The melody mirrors this: it steps down from one note to the next, leading into Tevir.
Example from the Torah
Bereishis 12:1
In Bereishis 12:1, the broader phrase structure includes Darga-Tevir patterns helping to break up the long instruction to Avraham.
Hear the melody
A synthesized rendering of the melodic shape, not a vocal recording. For a baal koreh's voice on a full aliyah, PocketTorah is a great free resource.
Hand signal (simanim)
Often confused with
Both are below-the-letter conjunctives. Munach is a single flat horizontal stroke; Darga is a zigzag with multiple bends.