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.
Drop down the second pipe, which leads to coin room H.
You've perfected the Koopa Paratroopa Bounce by now. Jump to the right over the long gap, and target the Koopa to bounce off its back and land on the bricks.
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 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.
If you know how to collect a Fire Flower in World 7-3, doing it here is easier than it looks. You still have to watch out for Spiny, but Lakitu can't harm you when you are standing on the ? block.
Lakitu disappears after you pass the pipe in this area.
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.