It depends on what you want the game to do, but one way doesn't require a huge scene. You can have one background image that doesn't actually change, but it created the illusion that you are moving because as time goes on more object are spawned off-screen and move constantly sideways until the go off the other end of the screen or are killed, then they are removed from the game. I'm sure you can find some basic game theory books or sites to help with this. Check our Cocos2D for the iPhone if you want to work on the iPhone. They also have a forum on their site too.I was just wondering how the graphics are made for side scrolling video games? How would you go about setting up a scene to make those long side scrolling games? I may need to do this soon. Any input would be great. Thanks.
Going off of what ArtOfWarfare said, this is a very common but simple technique used in many side scrollers (Jetpack Joyride, Funrun, etc). Basically you might have 2-3 "layers", the frontmost being the important game objects that the player can actually interact with, enemies, power ups, items, and such. The middle layer can be objects in the near background, like trees, rocks, buildings or whatever. And the last layer will usually be the setting of the game, like mountains, forest, cave, etc. And to make it all come together you simply make it so that the lower layers move slower than the top layers. It gives the illusion of traveling.