Cross

The cross is a concept first proposed in 1978 by Donald Taylor and is the first step for most layer by layer methods on 3x3x3[1]. It involves solving the four edges of one layer into place all at once. Beginner methods will often start by teaching the solver to place one piece at a time, but a more advanced cuber will be able to determine during inspection how to place all four edges at once. Forming the entire cross can always be done in 8 or fewer moves. In some cases, cubers will start a solve by building an extended cross, which involves a cross as well as one or more corneredge pairs.
Most beginners solve the cross on top, then once complete will rotate the cube so that the cross is now on the bottom. Then they will proceed to do F2L. Although you can solve the cross on any side, including the front, back, and the right or left sides, most cubers advise doing the cross on the bottom, as this provides greater visibility and lookahead for F2L, and also eliminates the need to do the cube rotation to position the cross at the bottom.
How to do the cross
The cross is almost completely intuitive. This means that there aren't many algorithms to help you. You just have to do it yourself.
If it's too difficult, simply place each edge in one by one, taking care not to destroy the other edges in place.
Your goal for the cross is to make your cube look exactly like the pictures above, with each nonwhite colored edge lined up with its respective color. The gray pieces are redundant.
If your cube looks like this, you can move on to the next step.
See also
 CFOP (Cross is the 1st step of the CFOP Method.)
 F2L (F2L is the main next step after Cross)
 XCross/Cross+1 (XCross/Cross+1 is Cross + 1st F2L pair)
 OLL/PLL (OLL/PLL solve the cube after Cross + F2L)
 EOLine (EOLine is another famous 1st step for other methods)
External links
 Cross Study  optimal move count stats for solving the cross.
 Rubik's Cube: Cross (Advanced)  YouTube video on solving the cross recommended by Feliks Zemdegs on Twitter (2012/11/26)
 Just Another Rubik's Cube Solver  Webbased solver that will give the optimum solutions for the cross.