Someone said, "Calculate the total delta H of the reaction and subtract the total delta H of the product from it. If you get a positive value, it radiates heat which means it's exothermic. If it is negative, heat is needed to get a reaction so it is endothermic." 

...shouldn't it be the other way around?? If you get a positive value, the enthalpy change is added to the reactants' side of the equation, i.e. more heat is absorbed, and therefore it's endothermic, and vice versa for exothermic ?

I am agreeing with you a negative delta H should be an exothermic reaction.

You are correct! The statement you mentioned is actually incorrect. The sign of the delta H value determines whether a reaction is endothermic or exothermic, not the result of a subtraction.

To determine whether a reaction is endothermic or exothermic, you need to observe the sign of the delta H value.

If the delta H value is positive, it means that more energy is absorbed from the surroundings than released, resulting in a net gain or increase in energy of the system. This indicates an endothermic reaction because it requires heat/energy input to occur.

On the other hand, if the delta H value is negative, it means that more energy is released into the surroundings than absorbed, resulting in a net loss or decrease in energy of the system. This indicates an exothermic reaction because it releases heat/energy to the surroundings.

So, it is the sign of the delta H value that determines whether a reaction is endothermic or exothermic, not the result of subtracting the delta H of the products from the delta H of the reactants.