If you're subletting an apartment, always pay your share of the rent to the tenant -- not to the landlord. As a subtenant, you haven't signed a lease with the landlord and you're under no legal obligation to pay your landlord any rent. You're only liable to the tenant for the amount you agreed on, while the tenant is liable to the landlord for the full rent.
So, if the tenant asks you to send your sublease rent checks to the landlord, politely decline. If you routinely pay the landlord and an issue arises with the apartment, a court could rule that you were, in effect, the tenant, and then hold you accountable for the problem.
