These shortcuts assume you already know how to solve the Rubik's Cube with the layer-by-layer method. Learn each shortcut whenever you feel comfortable with everything you have learned so far. The times are just recommendations, but you should follow your own schedule to fit your learning style.
2:00 and Up
Practice, practice, practice, with a timer if you want until you feel comfortable with learning another shortcut.
1:30- 4 Look Last Layer: Algorithms Required: 14 about 8 moves in length each
In order to do the final layer of the Rubik's cube more quickly, 4 look last layer combines steps to reduce the number of moves required. This method does require some memorization, but it cut my last layer time from 30 seconds to 13 seconds.
1:30- Finger tricks
With finger tricks, you can move the cube faster by using a single finger, instead of the whole hand, to turn a face. It is much faster and more comfortable once you learn. If you don't have a good cube, then this really won't work. If your using a really stiff cube, like a Rubik's brand, try adding vaseline. Vaseline will slowly dissolve the plastic, so it will make it looser and easier to turn. Once it turns easily, which may take up to a month, thoroughly clean it and remove the vaseline. Refer to "Buy a Speedcube" for other lubricants.
1:15- First Two Layers (F2L)
In the beginners method, you solve the first layer corners, then the edges. It is faster and more efficient to solve both the corners and the edges at the same time. You do this by pairing a corner with an edge, then inserting the pair. This is explained in the link.
1:10- Cross on Bottom
By solving the cross on the bottom of the cube, the cube does not need to be flipped to begin F2L, F2L lookahead is improved, and slow D turns are turned into fast U turns. It may be awkward at first, but as you get a feel for it, it will be much better.
1:00- Buy a Speedcube
If you are still using a standard store bought cube with nonadjustable tensions, please help yourself and buy a better cube. I recommend the Dayan Zhan Chi. If you apply Lubix your cube will turn more easily and smoothly. If you don't want to buy anything, use vegetable oil, but it WILL slowly dissolve your cube. Lubix does not dissolve the cube.
From Left: Dayan Zhanchi (stickered version), partially dissasembled Dayan Guhong, and a syringe of Lubix