StepMania/Gameplay

Installation
Download the game from the official StepMania website and run the executable. It will prompt you to install into your program files (which I suggest you do for ease of finding StepMania when you need to add songs, themes, etc. to your game) and will take up about 20 MB. Although this is the case, once you start getting into StepMania, the size of the game could EASILY jump into 5, 10, or even 50 GB if you download enough songs and other content for the game. Keep this in mind if you also install a copy of this to a small external flash drive, so you can weigh what would be your favorite songs to take with you if you decide to play outside your main StepMania game with one on any portable storage device (50 GB of songs would come about if you downloaded approximately 10-12,000 files, considering most files are about 2 or 3 minutes long, and have banners, backgrounds, etc.)

After the game is installed, the first thing you need to do is place a song file in the correct directory (C:\Program Files\StepMania\Songs\Song collection folder\The Song\), otherwise StepMania will have no songs to play (as it doesn't come with any). A better option would be to download a song package from Bluexoon or any other StepMania song hosting website, and install this pack into the C:\Program Files\StepMania\Songs\ folder, this way, you have a decent variety of songs to choose from, and a variation of difficulty so you can see how the game is played and what combinations are usually frequent in the songs you downloaded.

Initial configuration
You may want to make some changes to settings before you start playing the game, however, if you want to jump right in, skip to the next section. This is something you should try to avoid as the configurations you would change in the Stepmania options menu seriously effect how you play the game overall. Check out the StepMania walkthrough page for a detailed instruction of how and what to change in the Stepmania Options menu

The first changes you will probably want to make are the ones that affect how you read the arrows. This is referred to as "Speed" and it affects the length of time between notes and how fast they scroll across the screen. Some players like it very slow, which condenses the notes (decreased appearing BPM), and some find it easier to play when there is more space between notes (increased appearing BPM). These configurations can be made by pressing enter twice instead of a single time when selecting a song to bring up the options menu. Among other modifications, you will find the Speed settings (the first option on screen) in which you can change to whatever setting you desire. Although speed settings have two different categories, and what they do throughout the entire song, which is also covered in the StepMania walkthrough.

Starting a game
To start a game session after you have set up everything else the way you want it, simply select the Game Start, choose a difficulty (it REALLY doesn't matter which difficulty you choose, it effects nothing), choose a song / song difficulty (this difficulty is the one that dictates what you play), then wait for it to load, and play! After you complete a song (assuming you don't fail), depending on the song's length, you can select a 2nd, or 3rd level to play. A song's length effects a stage by doing the following:
 * Single Stage - if a song's length is anything less than 2:30, it is considered a single stage, which you can play three of before the game session ends
 * Long Stage - if the song is between 2:30 and 5:00, it is considered a long stage, which you can only play one of...and then play one more single stage before the end of the game session.
 * Marathon Stage - if a song's length is anything OVER 5 minutes (this could be anywhere from 5:00 to 10 hours long), it is considered a marathon stage. You can only play ONE of these stages before your game session ends.
 * Extra Stage - if you receive an AA on your last stage, you will be offered to play an extra stage, which is a stage that (under default options) forces you to play the hardest song difficulty in that area of songs (the pack) with the following modifications active: 1.5x, dark, reverse, and no recover. This stage is intended to be an additional time challenge to see how long you can survive a song with those settings on...in the event that you actually DO pass an extra stage, the score IS recorded and you are sent to the name entry screen as you usually would be.

Simply because, it is based on Dance Dance Revolution, where a person probably wouldn't dance for more than 5 or 6 minutes in more intense steps...and would usually take a break around that time. Advanced keyboard players will usually not have the feeling of getting tired after only 6 minutes of game play, and can sustain stamina for much longer (like the people who have completed the 1hr 54 minute JS challenge). But, restarting a new session takes about 15 seconds, so it really isn't all that much of a serious bother.
 * Why is it set up like this?