Dealing with kids' clothes at the season changes

Bonnie is in the middle of the only seasonally-related malady worse than pollen allergies: changing her children's clothing for the seasons. And she's hoping you have tips (because I sure don't). She says

"Every year I get the biggest headache trying to sort--size or season? Label or actual measurements? And now that I have my daughter it totally complicates...I am sure some parent has come up with an intelligent solution or system."

The only thing I know is that sorting by actual measurements ends up being better than sorting by the size on the label. But there has got to be some better way to do this than my method (3 big clear plastic containers, one for each of the sizes between my older son and my younger son), or at least some way to make me operationalize better so I'm not discovering big stashes of clothes in the size my younger one just grew out of.

Does anyone offer this as a professional service? I can't be the only one who would be willing to pay someone else to come in and manage our kids' clothing...

But I know there have to be some of you out there who have a true handle on this and can share for those of us who are struggling. Please, please share.