Enhancers that open the gate
The strongest dietary enhancer of non-heme iron is vitamin C, which keeps iron in the more absorbable ferrous state and can form a soluble complex with it; pairing a vitamin C source with a plant iron meal can meaningfully increase the fraction absorbed. A component of meat, poultry, and fish (the so-called meat factor) similarly boosts uptake of non-heme iron eaten in the same meal.
These effects act on non-heme iron specifically; heme iron from animal tissue is already well absorbed and less influenced by meal company.
Inhibitors and the timing workaround
Several common compounds bind iron and reduce absorption: tannins in tea and coffee, calcium (from dairy or supplements), phytates in whole grains and legumes, and some polyphenols. Because the effect is local and meal-specific, separating these from iron-rich meals (for example, taking tea between meals) limits the interference rather than eliminating the foods.
This is general educational information, not medical advice. People managing low iron should confirm strategy and any supplementation with a clinician, since needs and risks differ between individuals.