Position your plumber to the left of the first ground pipe. Then, when the Piranha Plant sinks and the Koopa walks to the left edge of the bricks, jump and bounce off of the Koopa to the top of the next pipe.
If your character is small by the end of this section, dash and jump between the pipe and the row of bricks to reach a Power-Up.
There is a hidden 1UP block right above the first "?" block. If you are Super or Fire Mario, you must hold Down + Jump in order to get it.
Altitude is more important than distance in the middle of this section. When you bounce off of the Koopa, take advantage of the extra air time and land on the bricks above.
You can use the invisible coin block below the 10-coin block to jump to the top of the brick platform, then you can jump off the paratroopa with less air time required.
You will also find an invisible coin block to the left of the small patch of land under the next set of bricks; this will be very difficult with mario but you can run and jump onto the invisible coin block and reveal a plant leading to coin heaven C. This will actually send you back earlier in the level but it is a good way to collect more coins.
You might remember a section of World 4-3 that was very much like this long open gap. Run with super speed and hop onto the blocks with all of the expert-jumping skill that you can muster.
The Koopa Paratroopa towards the end of this section hovers near the right edge of the gap, leaving a big space between the left edge and itself. Walk to the right until you see the Koopa, then back up, dash and jump. With luck, you'll hit it.
The bricks in the corners of the boxed-in area will keep you from hiding from the Fire-Bar.
At the first fire bar, you will be able to duck once until the path is clear.
At the second fire bar, you can't hide. You'll have to move very quickly, leaping from the left edge to the center to the right edge without stopping. This will be much more difficult if your hero is super sized.