Write the balanced chemical equation.
Convert all given reactant amounts to moles (use molar mass if given in grams).
Use the mole ratio from the balanced equation to convert each reactant’s moles to the moles of the other reactant it can react with (or to the possible moles of product).
Determine how many moles of each reactant are required to react with the available moles of the other reactant.
Compare available vs required amounts for each reactant.
The reactant that is used up first (available < required) is the limiting reagent.
The reactant that is not used up first is the excess reagent.
If needed, compute the theoretical yield using the limiting reagent’s mole ratio to the product.