Diamonds get dull after being worn a while.
I paid 60 bucks for some cleaning crap in the mall when I was about 17.
TOOTHPASTE SHINES DIAMONDS!
When My Fiance' gave me my ring, he said "Keep it up with toothpaste."
I know what you're thinking... "How many rings has this guy bought?!" haha
Anyway, I tried it and it worked like a charm.
Just put toothpaste on a toothbrush,
Rub in a circular motion on the entire piece of jewelry.
Run it under tap water and dry if off to watch it sparkle like new.