If listing out line items in your will isn't your thing, another option is to let siblings work it out themselves in advance. Yard sale stickers are one popular tool (think of those little round colored dots). Siblings can write their names and stick them on the back or bottom of the heirlooms they want.
The scrawl-and-stick ritual can become part of your family get-togethers, and it shouldn't be a one-time thing. People's tastes and wishes change. Say a grandchild is hugely enamored with a china set while she's a young girl, but as she ages it's her grandmother's sleek silver watch that she really adores. When the family goes back through their tags, she can take her marker off the one and add it to the other, paving the way for her aunt to stake a more solid claim on the china set she's been fond of since she was a child.
Tagging parties also give families a chance to relate all the interesting and loving memories tied to each heirloom, so everyone really understands the fantastic histories of each possession. Plus, the person preparing to pass on the items is secure in the knowledge that each heirloom will be treasured for years to come.
But maybe best of all, taking openly about who wants what gives people the chance to really weigh how much they want something against how their loved ones feel. If a daughter has known for years that her brother will be devastated if he doesn't receive their father's bedside lamp, then she won't be surprised when he wants to take it home. Otherwise, blindsided by her brother's claim, grief could convince her she desperately needs the lamp to remember her father by. By the time she realizes she doesn't really even like the lamp, she and her brother may have some foreboding fences to mend.