Most of my spoons are stainless steel which is a misnomer as they tend to be stained with tea constantly.
I found several videos to remove tea stains and I found this worked really well:
Instructions:
Cut a lemon in half. Squeeze lemon over the teaspoons. I used the lemon to also rub the lemon juice on any stained areas (you can also do this with a stainless steel mug). Leave for ten minutes.
Melt 2 tsp sugar in 1 cup of hot water. Pour over the teaspoons. Use steel wool to scrub off the remaining stains.
Note: Many of the comments with the video suggested not using steel wool as it scratches the surface and will incur more stains in the future.