First, you need a list of your items, with enough detail to determine the fair market value (typically, a description and quality -- good or fair (you can't deduct items in poor condition unless you have a signed appraisal). Then, you need to determine your own fair market value, you might get this by checking prices in a local thrift store, or for better quality items maybe look in consignment shops.
Then go into the Gifts to Charity section, enter the name of the charity and check the box for items. You do not need to list every item in the tax return, as long as you have a separate inventory. Select "household items and clothing" from the drop down menu, enter the date and value. On the next page you can enter the same general description, unless you want to enter a more specific description for specific items.
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