I will list things in general catagories - like "Miscellaneous Candy", "Miscellaneous Clothing", etc. and put an estimated value.

I was once told by an immigration officer (land border) that declaring nothing can be suspicious. He had an elderly couple who had spent a week in Toronto coming back to Michigan. He asked what they bought and they said "nothing". It was a little suspicious so they searched the vehicle and found 200 beanie babies they bought in Canada for resale in MI. If they had declared it they might have paid a few dollars in duty. By hiding it, they had them confiscated and were fined.

I prefer to list something even if it may not be requried by the confusing rules.