how do you know if a reactant or product is favored in a equilibrium equation?

An equilibrium reaction is affected by the following factors:
1. Effect of concentration: Increase in the concentration of reactants will favour the formation of products and vice-versa.
2. Effect of temperature: Increase in temperature will favour the formation of products if the reaction is endothermic whereas for an exothermic reaction the formation of reactants. And vice-versa.
3. Effect of pressure: If the reactants and products are in gaseous form, an increase in pressure will favour the formation of products if the volume of products is decreased. And vice-versa.

In fact if a reaction is in equilibrium any change made due to concentration, temperature and pressure will be nullified either going towards forward or backward.