Tiny plastic stools and low tables ARE the local restaurant. Some of Hanoi's best meals — bún chả, phở, bánh cuốn — come from these setups.
Look for places packed with locals at meal times (11:30–13:00 lunch, 18:00–20:00 dinner). Empty tourist-targeted spots often serve mediocre food at higher prices.
Point at what other diners are eating if the menu is intimidating. Most stalls specialize in one dish, so 'what they make' is what you'll get.