How to make sure you absorb enough iron: combine with vitamin C and don't drink tannin-containing beverages such as tea.
Iron is needed for a number of highly complex processes that continuously take place on a molecular level and that are indispensable to human life, e.g. the transportation of oxygen around your body!
Iron is required for the production of red blood cells (a process known as hematopoiesis), but it's also part of hemoglobin (that is the pigment of the red blood cells) binding to the oxygen and thus facilitating its transport from the lungs via the arteries to all cells throughout the body.
Once the oxygen is delivered the iron (as part of hemoglobin) binds the carbon dioxide which is then transported back to the lung from where it gets exhaled.
Vitamin C promotes the absorption of iron; when you eat green leafy vegetables, almonds or pumpkin seeds for iron, it's best to combine them with citrus.
Don't drink tea before, during or right after your meal, at least not the type which contains tannins. Tannins block the absorption of iron.