Go to the Forest Maze. Look around for those Wigglers that look like caterpillars. (Kind of)
Try to jump on its head or body and do it ten times without landing on the ground. You get a frog coin EVERY ten times you jump consecutively. You won't get a frog coin if you land on the ground before you jump on the Wiggler ten times in a row.
Next, you know that guy who sells fireworks I would recommend buying a few fireworks before ending the game and defeating Smithy. If you buy fireworks you get a better ending. Remember when you see the fireworks exploding in the air and see a mushroom, Fire Flower, or Star made out of the fireworks The more fireworks, you get one of those cool designs in the sky. There is a certain amount of fireworks you have to buy to get each design. Here is what I would say:
Mushroom:You barely or didn't even buy any Fireworks! (0-4)
Fire Flower:Pretty good. You got several fireworks. (5-9)
Star:Wow! That is a large amount of fireworks you got there! (10-infinity)
I'm not exactly sure how much fireworks you have to buy, but that is my estimates. I think you can throw out the fireworks and they will still count in the ending. I hope this helps!