A Charity Deduction Question

How would I handle multiple goods contributions to a charity that all would total over $250.00? In other words, say I donate clothing, appliances, etc., to the "XYZ Authorized Charity" in February and the total fair value is $150.00. No itemization/documentation needed. Then, in June or July, or somewhere down the road, I donate another $150.00 or $200.00 worth. My total for the year would be a figure that would necessitate itemization, documentation, etc., etc.. The charity, like most, does not give itemized documentation (unless they're really big buck contributions). What do I need to do to receive full value for my contributions? I apologize if the question may not be really clear, or the language correct, but this is the best I can present it. TIA