Super Mario 3D Land
World 1:
1-1 Star Coin 1: When you get to the crate blocking the broken bridge thing, go on the tightrope instead. The Star Coin will be in the middle of it.
Star Coin 2: Once you go to the check point, go left until you get to a tree. Climb it to get to a secret platform. Go into the pipe to go to an optical illusion area. To save trying to get it using 3D alone, just jump on the eye button to get a better view. Jump the gap to reach the Star Coin.
Star Coin 3: Once you go up the hill, go to the note block. Jump on it, climb the next two platforms, then take the tightrope across to the right.
1-3 Star Coin 1: Right off the bat, go straight to the binoculars and look through. On the curvy rock things, there is a toad. Look directly at him, and zoom in. He will throw a Star Coin. It lands above a note block. jump on that note block to reach it.
Star Coin 2: Once you get to the check point, continue right. Jump on the Rainbow note block. After you are on the clouds, make sure to hit the ? block. A star will come out. Continue on until the path ends. Jump off, making sure to get the Star Coin.
Star Coin 3: The last Star Coin is just above the lowest cloud. You can either jump onto the lower cloud then jump to get it when the cloud is under it, or you can jump straight into the Star Coin, making sure the cloud is under it.