At the start of the level, in plain sight. Simply jump from the slope that the Beach Koopa slid off of.
In plain sight near some Rexes. Simply jump from the slopes above.
In a blue Warp Pipe blocked off by some Flip Blocks. Spin Jump to break them. This will then bring you to a room with some Coins. The Dragon Coin will also be there, being blocked off by some Flip Blocks again. Once again, Spin Jump to break them.
In plain sight right before the Goal Pole. Simply jump to get it.
You can hold an extra item in the box at the top of the screen. To use it, press the SELECT button.
To pick up a shell, use the X or Y Button. To throw a shell upwards, look up and let go of the button