pre:

Begin the game by running right a short distance and bash the first "?" Block 
that comes into view, and this will give you your first Coin. Defeat the 
oncoming Goomba by stomping it (jumping on its head). There are three "?" 
Blocks next; bash the lower-left one and this will uncover a Super Mushroom. 
When it comes out of the block, it slides to the right. Let it drop down and 
after it bounces from the pipe on the right, it will come back towards you, and 
you can collect it to become Super Mario - Mario will increase in size and can 
therefore smash Brick Blocks. You can also take a hit from enemies when Super-
sized, but at the cost of reverting back to Regular size.

Bash the other two "?" Blocks, and go right, jumping over the first two green 
pipes. Stomp the Goomba that patrols between the second and third pipes, and 
jump over the third pipe, stomping another two Goombas there. You can go down 
the fourth pipe along to reach Coin Room 1 (see the Coin Rooms sub-section in 
the Bonus Areas section of this guide for more details), but by doing so you'll 
skip a good chunk of the level, and continuing on as normal means you can get a 
1-Up and many other goodies, so continue reading on if you choose to continue 
through the level as normal.

Now, after that fourth pipe, you can find a hidden 1-Up Mushroom by standing 
exactly six block spaces to the right of the pipe (if you look at the pattern 
in the ground you'll see what I mean by 'block spaces'), so that Mario is 
standing in front of the left side of the green mountain in the background, and 
jumping directly up to uncover an invisible block, out of which the 1-Up 
Mushroom will appear. You'll have to be very quick to go right and grab it, 
otherwise it can drop to the ground and slide into the bottomless pit on the 
right. For help on finding the hidden 1-Up Mushroom, here's an ASCII diagram to 
help:
_______________________________________________________________________________

                                +---+
                                |1UP|
+-------+                       +---+
|       |
+-------+
|       |
|       |
|       |
|       |
|       |
+-------+---------------------------------------+       +----------------------
                                                |       |
                                                |       |
                                                |       |
________________________________________________|_______|______________________

                  Key
                  ---
                  1UP = 1-Up Mushroom (inside Invisible Block)
_______________________________________________________________________________

After this, continue right and jump over the small pit. Next, you'll see two 
Goombas dropping down some platforms to the right. Wait for them to reach the 
ground, and take them out with a stomp each. Bash the "?" Block sandwiched 
between the two Brick Blocks, and this will uncover a Power-up (by this, I mean 
it will be a Super Mushroom if you're Regular Mario; or a Fire Flower if you're 
Super or Fire Mario). If it is a Fire Flower, you can collect it to make 
Mario/Luigi become Fire Mario/Luigi (denoted by a red-and-white colour scheme), 
and you can throw fireballs to fight most of your enemies.

Go right a little more, and make a running jump over another pit. Stomp the 
next two Goombas, then jump onto the top of the single Brick Block, and bash 
the "?" Block that is directly above it to get a Coin. Now drop back down to 
the ground and repeatedly bash that Brick Block you were just standing on - 
this is a Multi-Coin Block so by bashing it as quickly and repeatedly as you 
can, you'll get more Coins out of it, before it expires.

Right a little further, you'll have your first encounter with a Green Koopa 
Troopa (walking turtle-like enemy). If you've got Fire power, use a fireball to 
knock it out instantly, or stomp it and quickly kick the shell away. Above 
you'll see two adjoined Brick Blocks; bash the one on the right, and this will 
uncover a Starman! By grabbing this, you'll gain invincibility for a short 
period of time (denoted by the change in background music and Mario's clothes 
flickering), and you can walk into enemies to defeat them until the background 
music returns to normal.

Up next are four "?" Blocks; bash the three lower ones to get Coins from each 
of them, then jump onto the middle one and bash the block above that to get a 
Power-up. Defeat several more Goombas as you continue to head right, then jump 
onto the small Brick Block platform underneath the two "?" Blocks higher up. 
Bash both of these blocks for Coins. Go right, and climb your way over two 
small staircases. A little further on, do the same thing again, and carefully 
jump over the gap between the second pair of staircases.

Next is a small green pipe; if you went to the Coin Room noted a little earlier 
in this level's walkthrough, you'll emerge from this pipe to return to the main 
level after leaving that Coin Room. After that pipe, stomp or fry another two 
Goombas, and bash the "?" Block to get one last Coin. After this, jump your way 
up the large staircase, and from the top step, make a running leap over to the 
right to grab the flagpole, hopefully near the top to score more points. With 
that, you have finished the first level of the game.