The best strategy is to eat across all the tiers, because each shows you something different. Street markets and hawker stalls give you the everyday food culture at its most honest; pick the stall with the longest local queue and high turnover, which signals both quality and freshness. Family-run neighbourhood restaurants, especially at lunch when they serve set meals to workers, are where home-style cooking lives; the shabbier the decor and the shorter the menu, the better the odds.
Covered food markets and food courts are a great middle ground for sampling many things in one sitting, and in many countries they are institutions in their own right. Save fine dining for one or two meals where a good chef reinterprets the local classics; it helps you appreciate what the humble versions are doing.
The universal rules: walk two streets away from any major tourist sight before choosing, be suspicious of menus in six languages with photos, and ask locals where they would eat, not where tourists should.