The position of equilibrium tells you how much of the mixture is reactants and how much is products. Changing a condition shifts the position. If it shifts to the right, more products are present. If it shifts to the left, more reactants are present.
Temperature. Increasing the temperature moves the equilibrium in the endothermic direction. Decreasing the temperature moves it in the exothermic direction. The forward reaction in the Haber process is exothermic, so a higher temperature gives a lower yield of ammonia. Heating ammonium chloride shows the same idea: the endothermic direction, breaking down into gases, is favoured by heat.
Pressure. This only matters when gases are involved. Increasing the pressure moves the equilibrium towards the side with fewer gas molecules. In N2 + 3H2 ⇌ 2NH3 there are four gas molecules on the left and two on the right, so a higher pressure gives more ammonia.
Concentration. Increasing the concentration of a reactant shifts the equilibrium to the right, giving more products. Removing a product as it forms also shifts the equilibrium to the right.